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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.161 $ -->
 <reference id="ref.array">
  <title>Array Functions</title>
  <titleabbrev>Arrays</titleabbrev>
  <partintro>
   <simpara>
    These functions allow you to interact with and manipulate
    arrays in various ways. Arrays are essential for storing,
    managing, and operating on sets of variables.
   </simpara>
   <simpara>
    Simple and multi-dimensional arrays are supported, and may be
    either user created or created by another function.
    There are specific database handling functions for populating
    arrays from database queries, and several functions return arrays.
   </simpara>
  <para>
   Please see the <link linkend="language.types.array">Arrays</link>
   section of the manual for a detailed explanation of how arrays are
   implemented and used in PHP.
  </para>
   <para>
    See also <function>is_array</function>, <function>explode</function>,
    <function>implode</function>, <function>split</function>,
    and <function>join</function>.
   </para>
  </partintro>

  <refentry id="function.array">
   <refnamediv>
    <refname>array</refname>
    <refpurpose>
     Create an array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array</methodname>
      <methodparam choice="opt"><type>mixed</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     Returns an array of the parameters.  The parameters can be given
     an index with the <literal>=&gt;</literal> operator.
    </para>
    <para>
     <note>
      <para>
       <function>array</function> is a language construct used to
       represent literal arrays, and not a regular function.
      </para>
     </note>
    </para>
    <para>
     Syntax "index =&gt; values", separated by commas, define index
     and values. index may be of type string or numeric. When index is
     omitted, a integer index is automatically generated, starting
     at 0. If index is an integer, next generated index will
     be the biggest integer index + 1. Note that when two identical
     index are defined, the last overwrite the first.
    </para>
    <para>
     The following example demonstrates how to create a
     two-dimensional array, how to specify keys for associative
     arrays, and how to skip-and-continue numeric indices in normal
     arrays.
     <example>
      <title><function>array</function> example</title>
      <programlisting role="php">
<![CDATA[
$fruits = array (
    "fruits"  => array ("a"=>"orange", "b"=>"banana", "c"=>"apple"),
    "numbers" => array (1, 2, 3, 4, 5, 6),
    "holes"   => array ("first", 5 => "second", "third")
);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     <example>
      <title>Automatic index with <function>array</function></title>
      <programlisting role="php">
<![CDATA[
$array = array( 1, 1, 1, 1,  1, 8=>1,  4=>1, 19, 3=>13);
print_r($array);
]]>
      </programlisting>
      <para>
       will display :
       <screen role="php">
<![CDATA[
Array
(
    [0] => 1
    [1] => 1
    [2] => 1
    [3] => 13
    [4] => 1
    [8] => 1
    [9] => 19
)
]]>
       </screen>
      </para>
     </example>
     Note that index '3' is defined twice, and keep its final value of 13.
     Index 4 is defined after index 8, and next generated index (value 19)
     is 9, since biggest index was 8.
    </para>
    <para>
     This example creates a 1-based array.
     <example>
      <title>1-based index with <function>array</function></title>
      <programlisting role="php">
<![CDATA[
$firstquarter  = array(1 => 'January', 'February', 'March');
print_r($firstquarter);
]]>
      </programlisting>
      <para>
       will display :
       <screen>
<![CDATA[
Array
(
    [1] => 'January'
    [2] => 'February'
    [3] => 'March'
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     See also <function>array_pad</function>,
     <function>list</function>, and <function>range</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-change-key-case">
   <refnamediv>
    <refname>array_change_key_case</refname>
    <refpurpose>Returns an array with all string keys lowercased or uppercased</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_change_key_case</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>case</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_change_key_case</function> changes the
     keys in the <parameter>input</parameter> array to
     be all lowercase or uppercase. The change depends
     on the last optional <parameter>case</parameter>
     parameter. You can pass two constants there,
     <constant>CASE_UPPER</constant> and
     <constant>CASE_LOWER</constant>. The default is
     <constant>CASE_LOWER</constant>. The function will leave
     number indices as is.
    </para>
    <example>
     <title><function>array_change_key_case</function> example</title>
     <programlisting role="php">
<![CDATA[
$input_array = array("FirSt" => 1, "SecOnd" => 4);
print_r(array_change_key_case($input_array, CASE_UPPER);
]]>
     </programlisting>
     <para>
      The printout of the above program will be:
      <screen>
<![CDATA[
Array
(
    [FIRST] => 1
    [SECOND] => 2
)
]]>
      </screen>
     </para>
    </example>
   </refsect1>
  </refentry>

  <refentry id="function.array-chunk">
   <refnamediv>
    <refname>array_chunk</refname>
    <refpurpose>Split an array into chunks</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_chunk</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam><type>int</type><parameter>size</parameter></methodparam>
      <methodparam choice="opt"><type>bool</type><parameter>preserve_keys</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_chunk</function> splits the array into
     several arrays with <parameter>size</parameter> values
     in them. You may also have an array with less values
     at the end. You get the arrays as members of a
     multidimensional array indexed with numbers starting
     from zero.
    </para>
    <para>
     By setting the optional <parameter>preserve_keys</parameter>
     parameter to &true;, you can force PHP to preserve the original
     keys from the input array. If you specify &false; new number
     indices will be used in each resulting array with
     indices starting from zero. The default is &false;.
    </para>
    <example>
     <title><function>array_chunk</function> example</title>
     <programlisting role="php">
<![CDATA[
$input_array = array('a', 'b', 'c', 'd', 'e');
print_r(array_chunk($input_array, 2));
print_r(array_chunk($input_array, 2, TRUE));
]]>
     </programlisting>
     <para>
      The printout of the above program will be:
      <screen>
<![CDATA[
Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )

    [1] => Array
        (
            [0] => c
            [1] => d
        )

    [2] => Array
        (
            [0] => e
        )

)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )

    [1] => Array
        (
            [2] => c
            [3] => d
        )

    [2] => Array
        (
            [4] => e
        )

)
]]>
      </screen>
     </para>
    </example>
   </refsect1>
  </refentry>

  <refentry id="function.array-count-values">
   <refnamediv>
    <refname>array_count_values</refname>
    <refpurpose>Counts all the values of an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_count_values</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_count_values</function> returns an array using
     the values of the <parameter>input</parameter> array as keys and
     their frequency in <parameter>input</parameter> as values.
    </para>
    <para>
     <example>
      <title><function>array_count_values</function> example</title>
      <programlisting role="php">
<![CDATA[
$array = array (1, "hello", 1, "world", "hello");
print_r(array_count_values ($array));
]]>
      </programlisting>
      <para>
       The printout of the above program will be:
       <screen>
<![CDATA[
Array
(
    [1] => 2
    [hello] => 2
    [world] => 1
)
]]>
       </screen>
      </para>
     </example>
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-diff">
   <refnamediv>
    <refname>array_diff</refname>
    <refpurpose>Computes the difference of arrays</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_diff</methodname>
      <methodparam><type>array</type><parameter>array1</parameter></methodparam>
      <methodparam><type>array</type><parameter>array2</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter> ...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_diff</function> returns an array
     containing all the values of <parameter>array1</parameter>
     that are not present in any of the other arguments.
     Note that keys are preserved.
    </para>
    <para>
     <example>
      <title><function>array_diff</function> example</title>
      <programlisting role="php">
<![CDATA[
$array1 = array ("a" => "green", "red", "blue", "red");
$array2 = array ("b" => "green", "yellow", "red");
$result = array_diff ($array1, $array2);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This makes <varname>$result</varname> have
     <literal>array ("blue");</literal>. Multiple occurrences in
     $array1 are all treated the same way.
    </para>
    <note>
     <simpara>
      Two elements are considered equal if and only if
      <literal>(string) $elem1 === (string) $elem2</literal>. In words:
      when the string representation is the same.
      <!-- TODO: example of it... -->
     </simpara>
    </note>
    <warning>
     <simpara>
      This was broken in PHP 4.0.4!
      <!-- TODO: when exactly was this broken?... -->
     </simpara>
    </warning>
    <para>
     See also <function>array_intersect</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-filter">
   <refnamediv>
    <refname>array_filter</refname>
    <refpurpose>
     Filters elements of an array using a callback function
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_filter</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>callback</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_filter</function> returns an array
     containing all the elements of <parameter>input</parameter>
     filtered according a callback function. If the
     <parameter>input</parameter> is an associative array
     the keys are preserved.
    </para>
    <para>
     <example>
      <title><function>array_filter</function> example</title>
      <programlisting role="php">
<![CDATA[
function odd($var) {
    return ($var % 2 == 1);
}

function even($var) {
    return ($var % 2 == 0);
}

$array1 = array ("a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5);
$array2 = array (6, 7, 8, 9, 10, 11, 12);

echo "Odd :\n";
print_r(array_filter($array1, "odd"));
echo "Even:\n";
print_r(array_filter($array2, "even"));
]]>
      </programlisting>
      <para>
       The printout of the program above will be:
       <screen role="php">
<![CDATA[
Odd :
Array
(
    [a] => 1
    [c] => 3
    [e] => 5
)
Even:
Array
(
    [0] => 6
    [2] => 8
    [4] => 10
    [6] => 12
)
]]>
       </screen>
      </para>
     </example>
    </para>
    &note.func-callback;
    <para>
     See also <function>array_map</function> and
     <function>array_reduce</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-flip">
   <refnamediv>
    <refname>array_flip</refname>
    <refpurpose>Flip all the values of an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_flip</methodname>
      <methodparam><type>array</type><parameter>trans</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_flip</function> returns an <type>array</type> in flip
     order, i.e. keys from <parameter>trans</parameter> become values and
     <parameter>trans</parameter>'s values become keys.
    </para>
    <para>
     Note that the values of <parameter>trans</parameter> need to be valid
     keys, i.e. they need to be either <type>integer</type> or
     <type>string</type>. A warning will be emitted if a value has the wrong
     type, and the key/value pair in question <emphasis>will not be
     flipped</emphasis>.
    </para>
    <para>
     If a value has several occurrences, the latest key will be
     used as its values, and all others will be lost.
    </para>
    <para>
     <function>array_flip</function> returns &false;
     if it fails.
    </para>
    <para>
     <example>
      <title><function>array_flip</function> example</title>
      <programlisting role="php">
<![CDATA[
$trans = array_flip ($trans);
$original = strtr ($str, $trans);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     <example>
      <title><function>array_flip</function> example : collision</title>
      <programlisting role="php">
<![CDATA[
$trans = array ("a" => 1, "b" => 1, "c" => 2);
$trans = array_flip ($trans);
print_r($trans);
]]>
      </programlisting>
      <para>
       now $trans is :
       <screen>
<![CDATA[
Array
(
    [1] => b
    [2] => c
)
]]>
       </screen>
      </para>
     </example>
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-fill">
   <refnamediv>
    <refname>array_fill</refname>
    <refpurpose>Fill an array with values</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_fill</methodname>
      <methodparam><type>int</type><parameter>start_index</parameter></methodparam>
      <methodparam><type>int</type><parameter>num</parameter></methodparam>
      <methodparam><type>mixed</type><parameter>value</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_fill</function> fills an array with
     <parameter>num</parameter> entries of the value of the
     <parameter>value</parameter> parameter, keys starting at the
     <parameter>start_index</parameter> parameter.
    </para>
    <para>
     <example>
      <title><function>array_fill</function> example</title>
      <programlisting role="php">
<![CDATA[
$a = array_fill(5, 6, 'banana');
]]>
      </programlisting>
      <para>
       $a now has the following entries using <function>print_r</function>:
       <screen>
<![CDATA[
Array
(
    [5]  => banana
    [6]  => banana
    [7]  => banana
    [8]  => banana
    [9]  => banana
    [10] => banana
)
]]>
       </screen>
      </para>
     </example>
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-intersect">
   <refnamediv>
    <refname>array_intersect</refname>
    <refpurpose>Computes the intersection of arrays</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_intersect</methodname>
      <methodparam><type>array</type><parameter>array1</parameter></methodparam>
      <methodparam><type>array</type><parameter>array2</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter> ...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_intersect</function> returns an array
     containing all the values of <parameter>array1</parameter>
     that are present in all the arguments.
     Note that keys are preserved.
    </para>
    <para>
     <example>
      <title><function>array_intersect</function> example</title>
      <programlisting role="php">
<![CDATA[
$array1 = array ("a" => "green", "red", "blue");
$array2 = array ("b" => "green", "yellow", "red");
$result = array_intersect ($array1, $array2);
]]>
      </programlisting>
      <para>
       This makes <varname>$result</varname> have
       <screen role="php">
<![CDATA[
Array
(
    [a] => green
    [0] => red
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <note>
     <simpara>
      Two elements are considered equal if and only if
      <literal>(string) $elem1 === (string) $elem2</literal>. In words:
      when the string representation is the same.
      <!-- TODO: example of it... -->
     </simpara>
    </note>
    <warning>
     <simpara>
      This was broken in PHP 4.0.4!
      <!-- TODO: when exactly was this broken?... -->
     </simpara>
    </warning>
    <para>
     See also <function>array_diff</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-key-exists">
   <refnamediv>
    <refname>array_key_exists</refname>
    <refpurpose>Checks if the given key or index exists in the array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>bool</type><methodname>array_key_exists</methodname>
      <methodparam><type>mixed</type><parameter>key</parameter></methodparam>
      <methodparam><type>array</type><parameter>search</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_key_exists</function> returns &true; if the
     given <parameter>key</parameter> is set in the array.
     <parameter>key</parameter> can be any value possible
     for an array index.
    </para>
    <para>
     <example>
      <title><function>array_key_exists</function> example</title>
      <programlisting role="php">
<![CDATA[
$search_array = array("first" => 1, "second" => 4);
if (array_key_exists("first", $search_array)) {
    echo "The 'first' element is in the array";
}
]]>
      </programlisting>
     </example>
    </para>
    <note>
     <simpara>
      This name of this function is <function>key_exists</function>
      in PHP version 4.0.6.
     </simpara>
    </note>
    <para>
     See also <function>isset</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-keys">
   <refnamediv>
    <refname>array_keys</refname>
    <refpurpose>Return all the keys of an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_keys</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>
        search_value
       </parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_keys</function> returns the keys, numeric and
     string, from the <parameter>input</parameter> array.
    </para>
    <para>
     If the optional <parameter>search_value</parameter> is specified,
     then only the keys for that value are returned. Otherwise, all
     the keys from the <parameter>input</parameter> are returned.
    </para>
    <para>
     <example>
      <title><function>array_keys</function> example</title>
      <programlisting role="php">
<![CDATA[
$array = array (0 => 100, "color" => "red");
print_r(array_keys ($array));

$array = array ("blue", "red", "green", "blue", "blue");
print_r(array_keys ($array, "blue"));

$array = array ("color" => array("blue", "red", "green"), "size" => array("small", "medium", "large"));
print_r(array_keys ($array));
]]>
      </programlisting>
      <para>
       The printout of the program above will be:
       <screen>
<![CDATA[
Array
(
    [0] => 0
    [1] => color
)
Array
(
    [0] => 0
    [1] => 3
    [2] => 4
)
Array
(
    [0] => color
    [1] => size
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <note>
     <para>
      This function was added to PHP 4, below is an implementation for
      those still using PHP 3.
      <example>
       <title>
        Implementation of <function>array_keys</function> for PHP 3
        users
       </title>
       <programlisting role="php">
<![CDATA[
function array_keys ($arr, $term="") {
    $t = array();
    while (list($k,$v) = each($arr)) {
        if ($term && $v != $term) {
            continue;
        }
        $t[] = $k;
    }
    return $t;
}
]]>
       </programlisting>
      </example>
     </para>
    </note>
    <para>
     See also <function>array_values</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-map">
   <refnamediv>
    <refname>array_map</refname>
    <refpurpose>
     Applies the callback to the elements of the given arrays
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_map</methodname>
      <methodparam><type>mixed</type><parameter>callback</parameter></methodparam>
      <methodparam><type>array</type><parameter>arr1</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter>arr2...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_map</function> returns an array containing all
     the elements of <parameter>arr1</parameter> after applying the
     callback function to each one.  The number of parameters that the
     callback function accepts should match the number of arrays
     passed to the <function>array_map</function>
    </para>
    <para>
     <example>
      <title><function>array_map</function> example</title>
      <programlisting role="php">
<![CDATA[
function cube($n) {
    return $n*$n*$n;
}

$a = array(1, 2, 3, 4, 5);
$b = array_map("cube", $a);
print_r($b);
]]>
      </programlisting>
      <para>
       This makes <varname>$b</varname> have:
       <screen>
<![CDATA[
Array
(
    [0] => 1
    [1] => 8
    [2] => 27
    [3] => 64
    [4] => 125
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     <example>
      <title><function>array_map</function> - using more arrays</title>
      <programlisting role="php">
<![CDATA[
function show_Spanish($n, $m) {
    return "The number $n is called $m in Spanish";
}

function map_Spanish($n, $m) {
    return array ($n => $m);
}

$a = array(1, 2, 3, 4, 5);
$b = array("uno", "dos", "tres", "cuatro", "cinco");

$c = array_map("show_Spanish", $a, $b);
print_r($c);

$d = array_map("map_Spanish", $a , $b);
print_r($d);
]]>
      </programlisting>
      <para>
       This results:
       <screen>
<![CDATA[
// printout of $c
Array
(
    [0] => The number 1 is called uno in Spanish
    [1] => The number 2 is called dos in Spanish
    [2] => The number 3 is called tres in Spanish
    [3] => The number 4 is called cuatro in Spanish
    [4] => The number 5 is called cinco in Spanish
)

// printout of $d
Array
(
    [0] => Array
        (
            [1] => uno
        )

    [1] => Array
        (
            [2] => dos
        )

    [2] => Array
        (
            [3] => tres
        )

    [3] => Array
        (
            [4] => cuatro
        )

    [4] => Array
        (
            [5] => cinco
        )

)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     Usually when using two or more arrays, they should be of equal length
     because the callback function is applied in parallel to the corresponding
     elements.
     If the arrays are of unequal length, the shortest one will be extended
     with empty elements.
    </para>
    <para>
     An interesting use of this function is to construct an array of arrays,
     which can be easily performed by using &null;
     as the name of the callback function
    </para>
    <para>
     <example>
      <title>Creating an array of arrays</title>
      <programlisting role="php">
<![CDATA[
$a = array(1, 2, 3, 4, 5);
$b = array("one", "two", "three", "four", "five");
$c = array("uno", "dos", "tres", "cuatro", "cinco");

$d = array_map(null, $a, $b, $c);
print_r($d);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     The printout of the program above will be:
     <screen>
<![CDATA[
Array
(
    [0] => Array
        (
            [0] => 1
            [1] => one
            [2] => uno
        )

    [1] => Array
        (
            [0] => 2
            [1] => two
            [2] => dos
        )

    [2] => Array
        (
            [0] => 3
            [1] => three
            [2] => tres
        )

    [3] => Array
        (
            [0] => 4
            [1] => four
            [2] => cuatro
        )

    [4] => Array
        (
            [0] => 5
            [1] => five
            [2] => cinco
        )

)
]]>
     </screen>
    </para>
    <para>
     See also <function>array_filter</function> and
     <function>array_reduce</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-merge">
   <refnamediv>
    <refname>array_merge</refname>
    <refpurpose>Merge two or more arrays</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_merge</methodname>
      <methodparam><type>array</type><parameter>array1</parameter></methodparam>
      <methodparam><type>array</type><parameter>array2</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_merge</function> merges the elements of two or
     more arrays together so that the values of one are appended to
     the end of the previous one.  It returns the resulting array.
    </para>
    <para>
     If the input arrays have the same string keys, then the later
     value for that key will overwrite the previous one.  If, however,
     the arrays have the same numeric key, the later value will not
     overwrite the original value, but will be appended.
    </para>
    <para>
     <example>
      <title><function>array_merge</function> example</title>
      <programlisting role="php">
<![CDATA[
$array1 = array ("color" => "red", 2, 4);
$array2 = array ("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge ($array1, $array2);
]]>
      </programlisting>
      <para>
       The <literal>$result</literal> will be:
       <screen role="php">
<![CDATA[
Array
(
    [color] => green
    [0] => 2
    [1] => 4
    [2] => a
    [3] => b
    [shape] => trapezoid
    [4] => 4
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     See also <function>array_merge_recursive</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-merge-recursive">
   <refnamediv>
    <refname>array_merge_recursive</refname>
    <refpurpose>Merge two or more arrays recursively</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_merge_recursive</methodname>
      <methodparam><type>array</type><parameter>array1</parameter></methodparam>
      <methodparam><type>array</type><parameter>array2</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_merge_recursive</function> merges the elements of
     two or more arrays together so that the values of one are appended
     to the end of the previous one.  It returns the resulting array.
    </para>
    <para>
     If the input arrays have the same string keys, then the values for
     these keys are merged together into an array, and this is done
     recursively, so that if one of the values is an array itself, the
     function will merge it with a corresponding entry in another array
     too. If, however, the arrays have the same numeric key, the later
     value will not overwrite the original value, but will be appended.
    </para>
    <para>
     <example>
      <title><function>array_merge_recursive</function> example</title>
      <programlisting role="php">
<![CDATA[
$ar1 = array ("color" => array ("favorite" => "red"), 5);
$ar2 = array (10, "color" => array ("favorite" => "green", "blue"));
$result = array_merge_recursive ($ar1, $ar2);
]]>
      </programlisting>
      <para>
       The <literal>$result</literal> will be:
       <screen role="php">
<![CDATA[
Array
(
    [color] => Array
        (
            [favorite] => Array
                (
                    [0] => red
                    [1] => green
                )

            [0] => blue
        )

    [0] => 5
    [1] => 10
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     See also <function>array_merge</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-multisort">
   <refnamediv>
    <refname>array_multisort</refname>
    <refpurpose>Sort multiple or multi-dimensional arrays</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>bool</type><methodname>array_multisort</methodname>
      <methodparam><type>array</type><parameter>ar1</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>arg</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>...</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_multisort</function> can be used to sort several
     arrays at once or a multi-dimensional array according by one of
     more dimensions. It maintains key association when sorting.
    </para>
    <para>
     The input arrays are treated as columns of a table to be sorted
     by rows - this resembles the functionality of SQL ORDER BY
     clause. The first array is the primary one to sort by. The rows
     (values) in that array that compare the same are sorted by the
     next input array, and so on.
    </para>
    <para>
     The argument structure of this function is a bit unusual, but
     flexible. The very first argument has to be an
     array. Subsequently, each argument can be either an array or a
     sorting flag from the following lists.
    </para>
    <para>
     Sorting order flags:
     <itemizedlist>
      <listitem>
       <simpara>SORT_ASC - sort in ascending order</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_DESC - sort in descending order</simpara>
      </listitem>
     </itemizedlist>
    </para>
    <para>
     Sorting type flags:
     <itemizedlist>
      <listitem>
       <simpara>SORT_REGULAR - compare items normally</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_NUMERIC - compare items numerically</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_STRING - compare items as strings</simpara>
      </listitem>
     </itemizedlist>
    </para>
    <para>
     No two sorting flags of the same type can be specified after each
     array. The sorting flags specified after an array argument apply
     only to that array - they are reset to default SORT_ASC and
     SORT_REGULAR after before each new array argument.
    </para>
    <para>
     Returns &true; on success, &false;
     on failure.
    </para>
    <para>
     <example>
      <title>Sorting multiple arrays</title>
      <programlisting role="php">
<![CDATA[
$ar1 = array ("10", 100, 100, "a");
$ar2 = array (1, 3, "2", 1);
array_multisort ($ar1, $ar2);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     In this example, after sorting, the first array will contain 10,
     "a", 100, 100. The second array will contain 1, 1, "2", 3. The
     entries in the second array corresponding to the identical
     entries in the first array (100 and 100) were sorted as well.
    </para>
    <para>
     <example>
      <title>Sorting multi-dimensional array</title>
      <programlisting role="php">
<![CDATA[
$ar = array (array ("10", 100, 100, "a"), array (1, 3, "2", 1));
array_multisort ($ar[0], SORT_ASC, SORT_STRING,
                 $ar[1], SORT_NUMERIC, SORT_DESC);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     In this example, after sorting, the first array will contain 10,
     100, 100, "a" (it was sorted as strings in ascending order), and
     the second one will contain 1, 3, "2", 1 (sorted as numbers, in
     descending order).
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-pad">
   <refnamediv>
    <refname>array_pad</refname>
    <refpurpose>
     Pad array to the specified length with a value
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_pad</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam><type>int</type><parameter>pad_size</parameter></methodparam>
      <methodparam><type>mixed</type><parameter>pad_value</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_pad</function> returns a copy of the
     <parameter>input</parameter> padded to size specified by
     <parameter>pad_size</parameter> with value
     <parameter>pad_value</parameter>. If
     <parameter>pad_size</parameter> is positive then the array is
     padded on the right, if it's negative then on the left. If the
     absolute value of <parameter>pad_size</parameter> is less than or
     equal to the length of the <parameter>input</parameter> then no
     padding takes place.
    </para>
    <para>
     <example>
      <title><function>array_pad</function> example</title>
      <programlisting role="php">
<![CDATA[
$input = array (12, 10, 9);

$result = array_pad ($input, 5, 0);
// result is array (12, 10, 9, 0, 0)

$result = array_pad ($input, -7, -1);
// result is array (-1, -1, -1, -1, 12, 10, 9)

$result = array_pad ($input, 2, "noop");
// not padded
]]>
      </programlisting>
     </example>
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-pop">
   <refnamediv>
    <refname>array_pop</refname>
    <refpurpose>Pop the element off the end of array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>array_pop</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_pop</function> pops and returns the last value of
     the <parameter>array</parameter>, shortening the
     <parameter>array</parameter> by one element.
     If <parameter>array</parameter> is empty (or is not an array),
     &null; will be returned.
    </para>
    <para>
     <example>
      <title><function>array_pop</function> example</title>
      <programlisting role="php">
<![CDATA[
$stack = array ("orange", "banana", "apple", "raspberry");
$fruit = array_pop ($stack);
]]>
      </programlisting>
      <para>
       After this, <varname>$stack</varname> will have only 3 elements:
       <screen role="php">
<![CDATA[
Array
(
    [0] => orange
    [1] => banana
    [2] => apple
)
]]>
       </screen>
       and <literal>rasberry</literal> will be assigned to
       <varname>$fruit</varname>.
      </para>
     </example>
    </para>
    &return.falseproblem;
    <para>
     See also <function>array_push</function>,
     <function>array_shift</function>, and
     <function>array_unshift</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-push">
   <refnamediv>
    <refname>array_push</refname>
    <refpurpose>
     Push one or more elements onto the end of array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>array_push</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam><type>mixed</type><parameter>var</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_push</function> treats
     <parameter>array</parameter> as a stack, and pushes the passed
     variables onto the end of <parameter>array</parameter>. The
     length of <parameter>array</parameter> increases by the number of
     variables pushed. Has the same effect as:
     <programlisting role="php">
<![CDATA[
$array[] = $var;
]]>
     </programlisting>
     repeated for each <parameter>var</parameter>.
    </para>
    <para>
     Returns the new number of elements in the array.
    </para>
    <para>
     <example>
      <title><function>array_push</function> example</title>
      <programlisting role="php">
<![CDATA[
$stack = array ("orange", "banana");
array_push ($stack, "apple", "raspberry");
]]>
      </programlisting>
      <para>
       This example would result in <varname>$stack</varname> having
       the following elements:
       <screen role="php">
<![CDATA[
Array
(
    [0] => orange
    [1] => banana
    [2] => apple
    [3] => raspberry
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     See also <function>array_pop</function>,
     <function>array_shift</function>, and
     <function>array_unshift</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-rand">
   <refnamediv>
    <refname>array_rand</refname>
    <refpurpose>
     Pick one or more random entries out of an array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>array_rand</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>num_req</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_rand</function> is rather useful when you want to
     pick one or more random entries out of an array. It takes an
     <parameter>input</parameter> array and an optional argument
     <parameter>num_req</parameter> which specifies how many entries you
     want to pick - if not specified, it defaults to 1.
    </para>
    <para>
     If you are picking only one entry, <function>array_rand</function>
     returns the key for a random entry. Otherwise, it returns an array
     of keys for the random entries. This is done so that you can pick
     random keys as well as values out of the array.
    </para>
    <para>
     Don't forget to call <function>srand</function> to seed the random
     number generator.
    </para>
    <para>
     <example>
      <title><function>array_rand</function> example</title>
      <programlisting role="php">
<![CDATA[
srand ((float) microtime() * 10000000);
$input = array ("Neo", "Morpheus", "Trinity", "Cypher", "Tank");
$rand_keys = array_rand ($input, 2);
print $input[$rand_keys[0]]."\n";
print $input[$rand_keys[1]]."\n";
]]>
      </programlisting>
     </example>
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-reverse">
   <refnamediv>
    <refname>array_reverse</refname>
    <refpurpose>
     Return an array with elements in reverse order
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_reverse</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam choice="opt"><type>bool</type><parameter>preserve_keys</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_reverse</function> takes input
     <parameter>array</parameter> and returns a new array with the
     order of the elements reversed, preserving the keys if
     <parameter>preserve_keys</parameter> is &true;.
    </para>
    <para>
     <example>
      <title><function>array_reverse</function> example</title>
      <programlisting role="php">
<![CDATA[
$input  = array ("php", 4.0, array ("green", "red"));
$result = array_reverse ($input);
$result_keyed = array_reverse ($input, TRUE);
]]>
      </programlisting>
      <para>
       This makes both <varname>$result</varname> and
       <varname>$result_keyed</varname> have the same elements, but
       note the difference between the keys. The printout of
       <varname>$result</varname> and
       <varname>$result_keyed</varname> will be:
       <screen role="php">
<![CDATA[
Array
(
    [0] => Array
        (
            [0] => green
            [1] => red
        )

    [1] => 4
    [2] => php
)
Array
(
    [2] => Array
        (
            [0] => green
            [1] => red
        )

    [1] => 4
    [0] => php
)
]]>
       </screen>
      </para>

     </example>
    </para>
    <note>
     <para>
      The second parameter was added in PHP 4.0.3.
     </para>
    </note>
   </refsect1>
  </refentry>

  <refentry id="function.array-reduce">
   <refnamediv>
    <refname>array_reduce</refname>
    <refpurpose>
     Iteratively reduce the array to a single value using a callback
     function
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>array_reduce</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam><type>mixed</type><parameter>callback</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>initial</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_reduce</function> applies iteratively the
     <parameter>callback</parameter> function to the elements of the
     array <parameter>input</parameter>, so as to reduce the array to
     a single value. If the optional <parameter>initial</parameter> is
     available, it will be used at the beginning of the process, or as
     a final result in case the array is empty.
    </para>
    <para>
     <example>
      <title><function>array_reduce</function> example</title>
      <programlisting role="php">
<![CDATA[
function rsum($v, $w) {
    $v += $w;
    return $v;
}

function rmul($v, $w) {
    $v *= $w;
    return $v;
}

$a = array(1, 2, 3, 4, 5);
$x = array();
$b = array_reduce($a, "rsum");
$c = array_reduce($a, "rmul", 10);
$d = array_reduce($x, "rsum", 1);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This will result in <varname>$b</varname> containing
     <literal>15</literal>, <varname>$c</varname> containing
     <literal>1200</literal> (= 1*2*3*4*5*10), and
     <varname>$d</varname> containing <literal>1</literal>.
    </para>
    <para>
     See also <function>array_filter</function> and
     <function>array_map</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-shift">
   <refnamediv>
    <refname>array_shift</refname>
    <refpurpose>
     Shift an element off the beginning of array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>array_shift</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_shift</function> shifts the first value of the
     <parameter>array</parameter> off and returns it, shortening the
     <parameter>array</parameter> by one element and moving everything
     down.  If <parameter>array</parameter> is empty (or is not an
     array), &null; will be returned.
    </para>
    <para>
     <example>
      <title><function>array_shift</function> example</title>
      <programlisting role="php">
<![CDATA[
$stack = array ("orange", "banana", "apple", "raspberry");
$fruit = array_shift ($stack);
]]>
      </programlisting>
      <para>
       This would result in <varname>$stack</varname> having 3 elements left:
       <screen role="php">
<![CDATA[
Array
(
    [0] => banana
    [1] => apple
    [2] => raspberry
)
]]>
       </screen>
       and <literal>orange</literal> will be assigned to
       <varname>$fruit</varname>.
      </para>
     </example>
    </para>
    <para>
     See also <function>array_unshift</function>,
     <function>array_push</function>, and
     <function>array_pop</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-slice">
   <refnamediv>
    <refname>array_slice</refname>
    <refpurpose>Extract a slice of the array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_slice</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam><type>int</type><parameter>offset</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>
        length
       </parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_slice</function> returns the sequence of elements
     from the array <parameter>array</parameter> as specified by the
     <parameter>offset</parameter> and <parameter>length</parameter>
     parameters.
    </para>
    <para>
     If <parameter>offset</parameter> is positive, the sequence will
     start at that offset in the <parameter>array</parameter>.  If
     <parameter>offset</parameter> is negative, the sequence will
     start that far from the end of the <parameter>array</parameter>.
    </para>
    <para>
     If <parameter>length</parameter> is given and is positive, then
     the sequence will have that many elements in it. If
     <parameter>length</parameter> is given and is negative then the
     sequence will stop that many elements from the end of the
     array. If it is omitted, then the sequence will have everything
     from <parameter>offset</parameter> up until the end of the
     <parameter>array</parameter>.
    </para>
    <para>
     Note that <function>array_slice</function> will ignore array
     keys, and will calculate offsets and lengths based on the 
     actual positions of elements within the array.
    </para>
    <para>
     <example>
      <title><function>array_slice</function> examples</title>
      <programlisting role="php">
<![CDATA[
$input = array ("a", "b", "c", "d", "e");

$output = array_slice ($input, 2);      // returns "c", "d", and "e"
$output = array_slice ($input, 2, -1);  // returns "c", "d"
$output = array_slice ($input, -2, 1);  // returns "d"
$output = array_slice ($input, 0, 3);   // returns "a", "b", and "c"
]]>
      </programlisting>
     </example>
    </para>
    <para>
     See also <function>array_splice</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-splice">
   <refnamediv>
    <refname>array_splice</refname>
    <refpurpose>
     Remove a portion of the array and replace it with something
     else
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_splice</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
      <methodparam><type>int</type><parameter>offset</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>length</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter>
        replacement
       </parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_splice</function> removes the elements designated
     by <parameter>offset</parameter> and
     <parameter>length</parameter> from the
     <parameter>input</parameter> array, and replaces them with the
     elements of the <parameter>replacement</parameter> array, if
     supplied. It returns an array containing the extracted elements.
    </para>
    <para>
     If <parameter>offset</parameter> is positive then the start of
     removed portion is at that offset from the beginning of the
     <parameter>input</parameter> array.  If
     <parameter>offset</parameter> is negative then it starts that far
     from the end of the <parameter>input</parameter> array.
    </para>
    <para>
     If <parameter>length</parameter> is omitted, removes everything
     from <parameter>offset</parameter> to the end of the array.  If
     <parameter>length</parameter> is specified and is positive, then
     that many elements will be removed. If
     <parameter>length</parameter> is specified and is negative then
     the end of the removed portion will be that many elements from
     the end of the array.  Tip: to remove everything from
     <parameter>offset</parameter> to the end of the array when
     <parameter>replacement</parameter> is also specified, use
     <literal>count($input)</literal> for
     <parameter>length</parameter>.
    </para>
    <para>
     If <parameter>replacement</parameter> array is specified, then
     the removed elements are replaced with elements from this array.
     If <parameter>offset</parameter> and
     <parameter>length</parameter> are such that nothing is removed,
     then the elements from the <parameter>replacement</parameter>
     array are inserted in the place specified by the
     <parameter>offset</parameter>. Tip: if the replacement is just
     one element it is not necessary to put <literal>array()</literal>
     around it, unless the element is an array itself.
    </para>
    <para>
     The following equivalences hold:
     <programlisting role="php">
<![CDATA[
array_push ($input, $x, $y)     array_splice ($input, count ($input), 0,
                                             array ($x, $y))
array_pop ($input)              array_splice ($input, -1)
array_shift ($input)            array_splice ($input, 0, 1)
array_unshift ($input, $x, $y)  array_splice ($input, 0, 0, array ($x, $y))
$a[$x] = $y                     array_splice ($input, $x, 1, $y)
]]>
     </programlisting>
    </para>
    <para>
     Returns the array consisting of removed elements.
    </para>
    <para>
     <example>
      <title><function>array_splice</function> examples</title>
      <programlisting role="php">
<![CDATA[
$input = array ("red", "green", "blue", "yellow");
array_splice ($input, 2);
// $input is now array ("red", "green")

$input = array ("red", "green", "blue", "yellow");
array_splice ($input, 1, -1);
// $input is now array ("red", "yellow")

$input = array ("red", "green", "blue", "yellow");
array_splice ($input, 1, count($input), "orange");
// $input is now array ("red", "orange")

$input = array ("red", "green", "blue", "yellow");
array_splice ($input, -1, 1, array("black", "maroon"));
// $input is now array ("red", "green",
//          "blue", "black", "maroon")
]]>
      </programlisting>
     </example>
    </para>
    <para>
     See also <function>array_slice</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-sum">
   <refnamediv>
    <refname>array_sum</refname>
    <refpurpose>
     Calculate the sum of values in an array.
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>array_sum</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_sum</function> returns the sum of values
     in an array as an integer or float.
    </para>
    <para>
     <example>
      <title><function>array_sum</function> examples</title>
      <programlisting role="php">
<![CDATA[
$a = array(2, 4, 6, 8);
echo "sum(a) = ".array_sum($a)."\n";

$b = array("a"=>1.2,"b"=>2.3,"c"=>3.4);
echo "sum(b) = ".array_sum($b)."\n";
]]>
      </programlisting>
      <para>
       The printout of the program above will be:
       <screen role="php">
<![CDATA[
sum(a) = 20
sum(b) = 6.9
]]>
       </screen>
      </para>
     </example>
    </para>
    <note>
     <para>
      PHP versions prior to 4.0.6 modified the passed array
      itself and converted strings to numbers (which most
      of the time converted them to zero, depending on
      their value).
     </para>
    </note>
   </refsect1>
  </refentry>

  <refentry id="function.array-unique">
   <refnamediv>
    <refname>array_unique</refname>
    <refpurpose>Removes duplicate values from an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_unique</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_unique</function> takes input
     <parameter>array</parameter> and returns a new array
     without duplicate values.
    </para>
    <para>
     Note that keys are preserved. <function>array_unique</function> sorts
     the values treated as string at first, then will keep the first key
     encountered for every value, and ignore all following keys. It does not
     mean that the key of the first related value from the unsorted
     <parameter>array</parameter> will be kept.
    </para>
    <note>
     <simpara>
      Two elements are considered equal if and only if
      <literal>(string) $elem1 === (string) $elem2</literal>. In words:
      when the string representation is the same.
      <!-- TODO: example of it... -->
     </simpara>
     <simpara>
      The first element will be used.
     </simpara>
    </note>
    <warning>
     <simpara>
      This was broken in PHP 4.0.4!
      <!-- TODO: when exactly was this broken?... -->
     </simpara>
    </warning>
    <para>
     <example>
      <title><function>array_unique</function> example</title>
      <programlisting role="php">
<![CDATA[
$input = array ("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique ($input);
print_r($result);
]]>
      </programlisting>
      <para>
       This will output:
       <screen role="php">
<![CDATA[
Array
(
    [b] => green
    [1] => blue
    [2] => red
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     <example>
      <title><function>array_unique</function> and types</title>
      <programlisting role="php">
<![CDATA[
$input = array (4,"4","3",4,3,"3");
$result = array_unique ($input);
var_dump($result);
]]>
      </programlisting>
      <para>
       The printout of the program above will be (PHP 4.0.6):
       <screen role="php">
<![CDATA[
array(2) {
  [3]=>
  int(4)
  [4]=>
  int(3)
}
]]>
       </screen>
      </para>
     </example>
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-unshift">
   <refnamediv>
    <refname>array_unshift</refname>
    <refpurpose>
     Prepend one or more elements to the beginning of array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>array_unshift</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam><type>mixed</type><parameter>var</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>
        ...
       </parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_unshift</function> prepends passed elements to
     the front of the <parameter>array</parameter>. Note that the list
     of elements is prepended as a whole, so that the prepended
     elements stay in the same order.
    </para>
    <para>
     Returns the new number of elements in the
     <parameter>array</parameter>.
    </para>
    <para>
     <example>
      <title><function>array_unshift</function> example</title>
      <programlisting role="php">
<![CDATA[
$queue = array ("orange", "banana");
array_unshift ($queue, "apple", "raspberry");
]]>
      </programlisting>
      <para>
       This would result in <varname>$queue</varname> having the
       following elements:
       <screen role="php">
<![CDATA[
Array
(
    [0] => apple
    [1] => raspberry
    [2] => orange
    [3] => banana
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     See also <function>array_shift</function>,
     <function>array_push</function>, and
     <function>array_pop</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-values">
   <refnamediv>
    <refname>array_values</refname>
    <refpurpose>Return all the values of an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>array_values</methodname>
      <methodparam><type>array</type><parameter>input</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_values</function> returns all the values from the
     <parameter>input</parameter> array.
    </para>
    <para>
     <example>
      <title><function>array_values</function> example</title>
      <programlisting role="php">
<![CDATA[
$array = array ("size" => "XL", "color" => "gold");
print_r(array_values ($array));
]]>
      </programlisting>
      <para>
       This will output:
       <screen role="php">
<![CDATA[
Array
(
    [0] => XL
    [1] => gold
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <note>
     <para>
      This function was added to PHP 4, below is an implementation for
      those still using PHP 3.
      <example>
       <title>
        Implementation of <function>array_values</function> for PHP 3
        users
       </title>
       <programlisting role="php">
<![CDATA[
function array_values ($arr) {
    $t = array();
    while (list($k, $v) = each ($arr)) {
        $t[] = $v;
    }
    return $t;
}
]]>
       </programlisting>
      </example>
     </para>
    </note>
    <para>
     See also <function>array_keys</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-walk">
   <refnamediv>
    <refname>array_walk</refname>
    <refpurpose>
     Apply a user function to every member of an array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>array_walk</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam><type>string</type><parameter>func</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>userdata</parameter></methodparam>
     </methodsynopsis>
    <simpara>
     Applies the user-defined function named by <parameter>func</parameter>
     to each element of <parameter>array</parameter>.
     <parameter>func</parameter> will be passed array value as the
     first parameter and array key as the second parameter.  If
     <parameter>userdata</parameter> is supplied, it will be passed as
     the third parameter to the user function. <parameter>func</parameter>
     must be a user-defined function, and can't be a native PHP function.
     Thus, you can't use <function>array_walk</function> straight with
     <function>str2lower</function>, you must build a user-defined function
     with it first, and pass this function as argument.
    </simpara>
    &note.func-callback;
    <simpara>
     If <parameter>func</parameter> requires more than two or three
     arguments, depending on <parameter>userdata</parameter>, a
     warning will be generated each time
     <function>array_walk</function> calls
     <parameter>func</parameter>. These warnings may be suppressed by
     prepending the '@' sign to the <function>array_walk</function>
     call, or by using <function>error_reporting</function>.
    </simpara>
    <note>
     <para>
      If <parameter>func</parameter> needs to be working with the
      actual values of the array, specify that the first parameter of
      <parameter>func</parameter> should be passed by reference. Then
      any changes made to those elements will be made in the array
      itself.
     </para>
     <para>
      Modifying the array from inside <parameter>func</parameter>
      may cause unpredictable behavior.
     </para>
    </note>
    <note>
     <para>
      Passing the key and userdata to <parameter>func</parameter> was
      added in 4.0.
     </para>
     <para>
      In PHP 4 <function>reset</function> needs to be called as
      necessary since <function>array_walk</function> does not reset
      the array by default.
     </para>
    </note>
    <para>
     <example>
      <title><function>array_walk</function> example</title>
      <programlisting role="php">
<![CDATA[
$fruits = array ("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");

function test_alter (&$item1, $key, $prefix) {
    $item1 = "$prefix: $item1";
}

function test_print ($item2, $key) {
    echo "$key. $item2<br>\n";
}
echo "Before ...:\n";
array_walk ($fruits, 'test_print');
reset ($fruits);
array_walk ($fruits, 'test_alter', 'fruit');
echo "... and after:\n";
reset ($fruits);
array_walk ($fruits, 'test_print');
]]>
      </programlisting>
      <para>
       The printout of the program above will be:
       <screen role="php">
<![CDATA[
Before ...:
d. lemon
a. orange
b. banana
c. apple
... and after:
d. fruit: lemon
a. fruit: orange
b. fruit: banana
c. fruit: apple
]]>
       </screen>
      </para>
     </example>
    </para>
    <simpara>
     See also <function>each</function> and <function>list</function>.
    </simpara>
   </refsect1>
  </refentry>

  <refentry id="function.arsort">
   <refnamediv>
    <refname>arsort</refname>
    <refpurpose>
     Sort an array in reverse order and maintain index association
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>arsort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>sort_flags</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function sorts an array such that array indices maintain
     their correlation with the array elements they are associated
     with.  This is used mainly when sorting associative arrays where
     the actual element order is significant.
    </para>
    <example>
     <title><function>arsort</function> example</title>
     <programlisting role="php">
<![CDATA[
$fruits = array ("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
arsort ($fruits);
reset ($fruits);
while (list ($key, $val) = each ($fruits)) {
    echo "$key = $val\n";
}
]]>
     </programlisting>
     <para>
      This example would display:
      <screen>
<![CDATA[
a = orange
d = lemon
b = banana
c = apple
]]>
      </screen>
     </para>
    </example>
    <para>
     The fruits have been sorted in reverse alphabetical order, and
     the index associated with each element has been maintained.
    </para>
    <para>
     You may modify the behavior of the sort using the optional
     parameter <parameter>sort_flags</parameter>, for details
     see <function>sort</function>.
    </para>
    <para>
     See also <function>asort</function>, <function>rsort</function>,
     <function>ksort</function>, and <function>sort</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.asort">
   <refnamediv>
    <refname>asort</refname>
    <refpurpose>Sort an array and maintain index association</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>asort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>sort_flags</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function sorts an array such that array indices maintain
     their correlation with the array elements they are associated
     with.  This is used mainly when sorting associative arrays where
     the actual element order is significant.
    </para>
    <example>
     <title><function>asort</function> example</title>
     <programlisting role="php">
<![CDATA[
$fruits = array ("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
asort ($fruits);
reset ($fruits);
while (list ($key, $val) = each ($fruits)) {
    echo "$key = $val\n";
}
]]>
     </programlisting>
     <para>
      This example would display:
      <screen>
<![CDATA[
c = apple
b = banana
d = lemon
a = orange
]]>
      </screen>
     </para>
    </example>
    <para>
     The fruits have been sorted in alphabetical order, and the index
     associated with each element has been maintained.
    </para>
    <para>
     You may modify the behavior of the sort using the optional
     parameter <parameter>sort_flags</parameter>, for details
     see <function>sort</function>.
    </para>
    <para>
     See also <function>arsort</function>, <function>rsort</function>,
     <function>ksort</function>, and <function>sort</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.compact">
   <refnamediv>
    <refname>compact</refname>
    <refpurpose>
     Create array containing variables and their values
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>compact</methodname>
      <methodparam><type>mixed</type><parameter>varname</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>compact</function> takes a variable number of
     parameters. Each parameter can be either a string containing the
     name of the variable, or an array of variable names.  The array
     can contain other arrays of variable names inside it;
     <function>compact</function> handles it recursively.
    </para>
    <para>
     For each of these, <function>compact</function> looks for a
     variable with that name in the current symbol table and adds it
     to the output array such that the variable name becomes the key
     and the contents of the variable become the value for that key.
     In short, it does the opposite of <function>extract</function>.
     It returns the output array with all the variables added to it.
    </para>
    <para>
     Any strings that are not set will simply be skipped.
    </para>
    <para>
     <example>
      <title><function>compact</function> example</title>
      <programlisting role="php">
<![CDATA[
$city = "San Francisco";
$state = "CA";
$event = "SIGGRAPH";

$location_vars = array ("city", "state");

$result = compact ("event", "nothing_here", $location_vars);
]]>
      </programlisting>
      <para>
       After this, <varname>$result</varname> will be:
       <screen role="php">
<![CDATA[
Array
(
    [event] => SIGGRAPH
    [city] => San Francisco
    [state] => CA
)
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     See also <function>extract</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.count">
   <refnamediv>
    <refname>count</refname>
    <refpurpose>Count elements in a variable</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>count</methodname>
      <methodparam><type>mixed</type><parameter>var</parameter></methodparam>
     </methodsynopsis>
    <para>
     Returns the number of elements in <parameter>var</parameter>,
     which is typically an <type>array</type> (since anything else will have
     one element).
    </para>
    <para>
     If <parameter>var</parameter> is not an array, <literal>1</literal> will
     be returned (exception: <literal>count(&null;)</literal> equals
     <literal>0</literal>).
    </para>
    <warning>
     <para>
      <function>count</function> may return 0 for a variable that
      isn't set, but it may also return 0 for a variable that has
      been initialized with an empty array. Use
      <function>isset</function> to test if a variable is set.
     </para>
    </warning>
    <para>
     Please see the <link linkend="language.types.array">Arrays</link>
     section of the manual for a detailed explanation of how arrays
     are implemented and used in PHP.
    </para>
    <para>
     <example>
      <title><function>count</function> example</title>
      <programlisting role="php">
      <!-- TODO: examples about count(null), count(false), count(object).. -->
<![CDATA[
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
$result = count ($a);
// $result == 3

$b[0] = 7;
$b[5] = 9;
$b[10] = 11;
$result = count ($b);
// $result == 3;
]]>
      </programlisting>
     </example>
    </para>
   <note>
    <para>
     The <function>sizeof</function> function is an
     <link linkend="aliases">alias</link> for <function>count</function>.
    </para>
   </note>
    <para>
     See also <function>is_array</function>,
     <function>isset</function>, and
     <function>strlen</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.current">
   <refnamediv>
    <refname>current</refname>
    <refpurpose>Return the current element in an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>current</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     Every array has an internal pointer to its "current" element,
     which is initialized to the first element inserted into the
     array.
    </para>
    <para>
     The <function>current</function> function simply returns the
     array element that's currently being pointed by the internal
     pointer.  It does not move the pointer in any way.  If the
     internal pointer points beyond the end of the elements list,
     <function>current</function> returns &false;.
     <warning>
      <para>
       If the array contains empty elements (0 or "", the empty
       string) then this function will return &false;
       for these elements as well.  This makes it impossible to
       determine if you are really at the end of the list in such
       an array using <function>current</function>.  To properly
       traverse an array that may contain empty elements, use the
       <function>each</function> function.
      </para>
     </warning>
    </para>
    <para>
     See also <function>end</function>, <function>next</function>,
     <function>prev</function>, and <function>reset</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.each">
   <refnamediv>
    <refname>each</refname>
    <refpurpose>
     Return the current key and value pair from an array and advance
     the array cursor
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>each</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     Returns the current key and value pair from the array
     <parameter>array</parameter> and advances the array cursor. This
     pair is returned in a four-element array, with the keys
     <emphasis>0</emphasis>, <emphasis>1</emphasis>,
     <emphasis>key</emphasis>, and
     <emphasis>value</emphasis>. Elements <emphasis>0</emphasis> and
     <emphasis>key</emphasis> contain the key name of the array
     element, and <emphasis>1</emphasis> and
     <emphasis>value</emphasis> contain the data.
    </para>
    <para>
     If the internal pointer for the array points past the end of the
     array contents, <function>each</function> returns
     &false;.
    </para>
    <para>
     <example>
      <title><function>each</function> examples</title>
      <programlisting role="php">
<![CDATA[
$foo = array ("bob", "fred", "jussi", "jouni", "egon", "marliese");
$bar = each ($foo);
]]>
      </programlisting>
      <para>
       <varname>$bar</varname> now contains the following key/value
       pairs:
       <itemizedlist spacing="compact">
        <listitem><simpara>0 =&gt; 0</simpara></listitem>
        <listitem><simpara>1 =&gt; 'bob'</simpara></listitem>
        <listitem><simpara>key =&gt; 0</simpara></listitem>
        <listitem><simpara>value =&gt; 'bob'</simpara></listitem>
       </itemizedlist>
       <programlisting role="php">
<![CDATA[
$foo = array ("Robert" => "Bob", "Seppo" => "Sepi");
$bar = each ($foo);
]]>
       </programlisting>
      </para>
      <para>
       <varname>$bar</varname> now contains the following key/value
       pairs:
       <itemizedlist spacing="compact">
        <listitem><simpara>0 =&gt; 'Robert'</simpara></listitem>
        <listitem><simpara>1 =&gt; 'Bob'</simpara></listitem>
        <listitem><simpara>key =&gt; 'Robert'</simpara></listitem>
        <listitem><simpara>value =&gt; 'Bob'</simpara></listitem>
       </itemizedlist>
      </para>
     </example>
    </para>
    <para>
     <function>each</function> is typically used in conjunction with
     <function>list</function> to traverse an array; for instance,
     <varname>$HTTP_POST_VARS</varname>:
     <example>
      <title>
       Traversing <varname>$HTTP_POST_VARS</varname> with
       <function>each</function>
      </title>
      <programlisting role="php">
<![CDATA[
echo "Values submitted via POST method:<br>";
reset ($HTTP_POST_VARS);
while (list ($key, $val) = each ($HTTP_POST_VARS)) {
    echo "$key => $val<br>";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     After <function>each</function> has executed, the array cursor
     will be left on the next element of the array, or on the last
     element if it hits the end of the array. You have to use
     <function>reset</function> if you want to traverse the array
     again using each.
    </para>
    <para>
     See also <function>key</function>, <function>list</function>,
     <function>current</function>, <function>reset</function>,
     <function>next</function>, and <function>prev</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.end">
   <refnamediv>
    <refname>end</refname>
    <refpurpose>
     Set the internal pointer of an array to its last element
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>end</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>end</function> advances <parameter>array</parameter>'s
     internal pointer to the last element, and returns that element.
    </para>
    <para>
     See also <function>current</function>,
     <function>each</function>,
     <function>next</function>, and <function>reset</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.extract">
   <refnamediv>
    <refname>extract</refname>
    <refpurpose>
     Import variables into the current symbol table from an array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>extract</methodname>
      <methodparam><type>array</type><parameter>var_array</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>extract_type</parameter></methodparam>
      <methodparam choice="opt"><type>string</type><parameter>prefix</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function is used to import variables from an array into the
     current symbol table.  It takes an associative array
     <parameter>var_array</parameter> and treats keys as variable
     names and values as variable values.  For each key/value pair it
     will create a variable in the current symbol table, subject to
     <parameter>extract_type</parameter> and
     <parameter>prefix</parameter> parameters.
    </para>
    <note>
     <para>
      Since version 4.0.5 this function returns the number of
      variables extracted.
     </para>
    </note>
    <note>
     <para>
      EXTR_IF_EXISTS and EXTR_PREFIX_IF_EXISTS was introduced in version 4.2.0.
     </para>
    </note>
    <para>
     <function>extract</function> checks each key to see whether it
     constitutes a valid variable name and also for collisions with
     existing variables in the symbol table. The way invalid/numeric
     keys and collisions are treated is determined by
     <parameter>extract_type</parameter>. It can be one of the
     following values:
     <variablelist>
      <varlistentry>
       <term>EXTR_OVERWRITE</term>
       <listitem>
        <simpara>
         If there is a collision, overwrite the existing variable.
        </simpara>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term>EXTR_SKIP</term>
       <listitem>
        <simpara>
         If there is a collision, don't overwrite the existing
         variable.
        </simpara>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term>EXTR_PREFIX_SAME</term>
       <listitem>
        <simpara>If there is a collision, prefix the variable name with
        <parameter>prefix</parameter>.
        </simpara>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term>EXTR_PREFIX_ALL</term>
       <listitem>
        <simpara>
         Prefix all variable names with
         <parameter>prefix</parameter>. Since PHP 4.0.5 this includes
         numeric ones as well.
        </simpara>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term>EXTR_PREFIX_INVALID</term>
       <listitem>
        <simpara>
         Only prefix invalid/numeric variable names with
         <parameter>prefix</parameter>. This flag was added in
         PHP 4.0.5.
        </simpara>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term>EXTR_IF_EXISTS</term>
       <listitem>
        <simpara>
         Only overwrite the variable if it already exists in the
         current symbol table, otherwise do nothing.  This is useful
         for defining a list of valid variables and then extracting
         only those variables you have defined out of $_REQUEST, for
         example.  This flag was added in PHP 4.2.0.
        </simpara>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term>EXTR_PREFIX_IF_EXISTS</term>
       <listitem>
        <simpara>
         Only create prefixed variable names if the non-prefixed version
         of the same variable exists in the current symbol table.  This
         flag was added in PHP 4.2.0.
        </simpara>
       </listitem>
      </varlistentry>
     </variablelist>
    </para>
    <para>
     If <parameter>extract_type</parameter> is not specified, it is
     assumed to be EXTR_OVERWRITE.
    </para>
    <para>
     Note that <parameter>prefix</parameter> is only required if
     <parameter>extract_type</parameter> is EXTR_PREFIX_SAME,
     EXTR_PREFIX_ALL, EXTR_PREFIX_INVALID or EXTR_PREFIX_IF_EXISTS. If 
     the prefixed result is not a valid variable name, it is not 
     imported into the symbol table.
    </para>
    <para>
     <function>extract</function> returns the number of variables
     successfully imported into the symbol table.
    </para>
    <para>
     A possible use for extract is to import into the symbol table
     variables contained in an associative array returned by
     <function>wddx_deserialize</function>.
    </para>
    <para>
     <example>
      <title><function>extract</function> example</title>
      <programlisting role="php">
<![CDATA[
<?php

/* Suppose that $var_array is an array returned from
   wddx_deserialize */

$size = "large";
$var_array = array ("color" => "blue",
                    "size"  => "medium",
                    "shape" => "sphere");
extract ($var_array, EXTR_PREFIX_SAME, "wddx");

print "$color, $size, $shape, $wddx_size\n";

?>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     The above example will produce:
     <programlisting>
<![CDATA[
blue, large, sphere, medium
]]>
     </programlisting>
    </para>
    <para>
     The <varname>$size</varname> wasn't overwritten, because we
     specified EXTR_PREFIX_SAME, which resulted in
     <varname>$wddx_size</varname> being created.  If EXTR_SKIP was
     specified, then $wddx_size wouldn't even have been created.
     EXTR_OVERWRITE would have caused <varname>$size</varname> to have
     value "medium", and EXTR_PREFIX_ALL would result in new variables
     being named <varname>$wddx_color</varname>,
     <varname>$wddx_size</varname>, and
     <varname>$wddx_shape</varname>.
    </para>
    <para>
     You must use an associative array, a numerically indexed array
     will not produce results unless you use EXTR_PREFIX_ALL or 
     EXTR_PREFIX_INVALID.
    </para>
    <para>
     See also <function>compact</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.in-array">
   <refnamediv>
    <refname>in_array</refname>
    <refpurpose>Return &true; if a value exists in an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>bool</type><methodname>in_array</methodname>
      <methodparam><type>mixed</type><parameter>needle</parameter></methodparam>
      <methodparam><type>array</type><parameter>haystack</parameter></methodparam>
      <methodparam choice="opt"><type>bool</type><parameter>strict</parameter></methodparam>
     </methodsynopsis>
    <para>
     Searches <parameter>haystack</parameter> for
     <parameter>needle</parameter> and returns &true;
     if it is found in the array, &false; otherwise.
    </para>
    <para>
     If the third parameter <parameter>strict</parameter> is set to
     &true; then the <function>in_array</function> function
     will also check the <link linkend="language.types">types</link> of
     the <parameter>needle</parameter> in the <parameter>haystack</parameter>.
    </para>
    <note>
     <para>
      If <parameter>needle</parameter> is a string, the comparison is done in
      a case-sensitive manner.
     </para>
    </note>
    <note>
     <para>
      In PHP versions before 4.2.0 <parameter>needle</parameter> was not
      allowed to be an array.
     </para>
    </note>
    <para>
     <example>
      <title><function>in_array</function> example</title>
      <programlisting role="php">
<![CDATA[
$os = array ("Mac", "NT", "Irix", "Linux");
if (in_array ("Irix", $os)) {
    print "Got Irix";
}
if (in_array ("mac", $os)) {
    print "Got mac";
}
]]>
      </programlisting>
      <para>
       The second condition fails because <function>in_array</function>
       is case-sensitive, so the program above will display:
       <screen role="php">
<![CDATA[
Got Irix
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     <example>
      <title><function>in_array</function> with strict example</title>
      <programlisting role="php">
<![CDATA[
<?php
$a = array('1.10', 12.4, 1.13);

if (in_array('12.4', $a, TRUE))
    echo "'12.4' found with strict check\n";
if (in_array(1.13, $a, TRUE))
    echo "1.13 found with strict check\n";
?>
]]>
      </programlisting>
      <para>
       This will display:
       <screen role="php">
<![CDATA[
1.13 found with strict check
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     <example>
      <title><function>in_array</function> with an array as needle</title>
      <programlisting role="php">
<![CDATA[
<?php
$a = array(array('p', 'h'), array('p', 'r'), 'o');

if (in_array(array ('p', 'h'), $a))
    echo "'ph' is found\n";
if (in_array(array ('f', 'i'), $a))
    echo "'fi' is not found\n";
if (in_array('o', $a))
    echo "'o' is found\n";
?>

// This will output:

'ph' is found
'o' is found
]]>
      </programlisting>
     </example>
    </para>
    <para>
     See also <function>array_search</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.array-search">
   <refnamediv>
    <refname>array_search</refname>
    <refpurpose>
     Searches the array for a given value and returns the
     corresponding key if successful
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>array_search</methodname>
      <methodparam><type>mixed</type><parameter>needle</parameter></methodparam>
      <methodparam><type>array</type><parameter>haystack</parameter></methodparam>
      <methodparam choice="opt"><type>bool</type><parameter>strict</parameter></methodparam>
     </methodsynopsis>
    <para>
     Searches <parameter>haystack</parameter> for
     <parameter>needle</parameter> and returns the key if it is found in
     the array, &false; otherwise.
    </para>
    <para>
     If the optional third parameter <parameter>strict</parameter> is set to
     &true; then the <function>array_search</function>
     will also check the types of the <parameter>needle</parameter>
     in the <parameter>haystack</parameter>.
    </para>
    &return.falseproblem;
    <para>
     See also <function>in_array</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.key">
   <refnamediv>
    <refname>key</refname>
    <refpurpose>Fetch a key from an associative array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>key</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>key</function> returns the index element of the
     current array position.
    </para>
    <para>
     See also <function>current</function> and <function>next</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.krsort">
   <refnamediv>
    <refname>krsort</refname>
    <refpurpose>Sort an array by key in reverse order</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>krsort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>sort_flags</parameter></methodparam>
     </methodsynopsis>
    <para>
     Sorts an array by key in reverse order, maintaining key to data
     correlations. This is useful mainly for associative arrays.
     <example>
      <title><function>krsort</function> example</title>
      <programlisting role="php">
<![CDATA[
$fruits = array ("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
krsort ($fruits);
reset ($fruits);
while (list ($key, $val) = each ($fruits)) {
    echo "$key = $val\n";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
<![CDATA[
d = lemon
c = apple
b = banana
a = orange
]]>
     </screen>
    </para>
    <para>
     You may modify the behavior of the sort using the optional
     parameter <parameter>sort_flags</parameter>, for details
     see <function>sort</function>.
    </para>
    <simpara>
     See also <function>asort</function>, <function>arsort</function>,
     <function>ksort</function>, <function>sort</function>,
     <function>natsort</function>, and <function>rsort</function>.
    </simpara>
   </refsect1>
  </refentry>

  <refentry id="function.ksort">
   <refnamediv>
    <refname>ksort</refname>
    <refpurpose>Sort an array by key</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>ksort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>sort_flags</parameter></methodparam>
     </methodsynopsis>
    <para>
     Sorts an array by key, maintaining key to data correlations. This
     is useful mainly for associative arrays.
     <example>
      <title><function>ksort</function> example</title>
      <programlisting role="php">
<![CDATA[
$fruits = array ("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
ksort ($fruits);
reset ($fruits);
while (list ($key, $val) = each ($fruits)) {
    echo "$key = $val\n";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
<![CDATA[
a = orange
b = banana
c = apple
d = lemon
]]>
     </screen>
    </para>
    <para>
     You may modify the behavior of the sort using the optional
     parameter <parameter>sort_flags</parameter>, for details
     see <function>sort</function>.
    </para>
    <simpara>
     See also <function>asort</function>, <function>arsort</function>,
     <function>krsort</function>, <function>uksort</function>,
     <function>sort</function>, <function>natsort</function>, and
     <function>rsort</function>.
    </simpara>
    <note>
     <para>
      The second parameter was added in PHP 4.
     </para>
    </note>
   </refsect1>
  </refentry>

  <refentry id="function.list">
   <refnamediv>
    <refname>list</refname>
    <refpurpose>
     Assign variables as if they were an array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>list</methodname>
      <methodparam rep="repeat"><type>mixed</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     Like <function>array</function>, this is not really a function,
     but a language construct.  <function>list</function> is used to
     assign a list of variables in one operation.
     <example>
      <title><function>list</function> example</title>
      <programlisting role="php">
<![CDATA[
<table>
 <tr>
  <th>Employee name</th>
  <th>Salary</th>
 </tr>

<?php

$result = mysql_query ("SELECT id, name, salary FROM employees",$conn);
while (list ($id, $name, $salary) = mysql_fetch_row ($result)) {
    print (" <tr>\n".
           "  <td><a href=\"info.php?id=$id\">$name</a></td>\n".
           "  <td>$salary</td>\n".
           " </tr>\n");
}

?>

</table>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     See also <function>each</function> and <function>array</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.natsort">
   <refnamediv>
    <refname>natsort</refname>
    <refpurpose>
     Sort an array using a "natural order" algorithm
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>natsort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function implements a sort algorithm that orders
     alphanumeric strings in the way a human being would.  This is
     described as a "natural ordering". An example of the difference
     between this algorithm and the regular computer string sorting
     algorithms (used in <function>sort</function>) can be seen below:
    </para>
    <para>
     <example>
      <title><function>natsort</function> example</title>
      <programlisting role="php">
<![CDATA[
$array1 = $array2 = array ("img12.png", "img10.png", "img2.png", "img1.png");

sort($array1);
echo "Standard sorting\n";
print_r($array1);

natsort($array2);
echo "\nNatural order sorting\n";
print_r($array2);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     The code above will generate the following output:
    </para>
    <para>
     <screen>
<![CDATA[
Standard sorting
Array
(
    [0] => img1.png
    [1] => img10.png
    [2] => img12.png
    [3] => img2.png
)

Natural order sorting
Array
(
    [3] => img1.png
    [2] => img2.png
    [1] => img10.png
    [0] => img12.png
)
]]>
     </screen>
     For more information see: Martin Pool's <ulink
     url="&url.strnatcmp;">Natural Order String Comparison</ulink>
     page.
    </para>
    <para>
     See also <function>natcasesort</function>,
     <function>strnatcmp</function>, and
     <function>strnatcasecmp</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.natcasesort">
   <refnamediv>
    <refname>natcasesort</refname>
    <refpurpose>
     Sort an array using a case insensitive "natural order" algorithm
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>natcasesort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function implements a sort algorithm that orders
     alphanumeric strings in the way a human being would.  This is
     described as a "natural ordering".
    </para>
    <para>
     <function>natcasesort</function> is a case insensitive version of
     <function>natsort</function>.  See <function>natsort</function>
     for an example of the difference between this algorithm and the
     regular computer string sorting algorithms.
    </para>
    <para>
     For more information see: Martin Pool's <ulink
     url="&url.strnatcmp;">Natural Order String Comparison</ulink>
     page.
    </para>
    <para>
     See also <function>sort</function>,
     <function>natsort</function>,
     <function>strnatcmp</function>, and
     <function>strnatcasecmp</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.next">
   <refnamediv>
    <refname>next</refname>
    <refpurpose>
     Advance the internal array pointer of an array
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>next</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     Returns the array element in the next place that's pointed by the
     internal array pointer, or &false; if
     there are no more elements.
    </para>
    <para>
     <function>next</function> behaves like
     <function>current</function>, with one difference.  It advances
     the internal array pointer one place forward before returning the
     element.  That means it returns the next array element and
     advances the internal array pointer by one.  If advancing the
     internal array pointer results in going beyond the end of the
     element list, <function>next</function> returns &false;.
     <warning>
      <para>
       If the array contains empty elements, or elements that have a key
       value of 0 then this function will return &false;
       for these elements as well.  To properly traverse an array which
       may contain empty  elements or elements with key values of 0 see the
       <function>each</function> function.
      </para>
     </warning>
    </para>
    <para>
     See also
     <function>current</function>, <function>end</function>,
     <function>prev</function>, and <function>reset</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.pos">
   <refnamediv>
    <refname>pos</refname>
    <refpurpose>Get the current element from an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>pos</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <simpara>
     This is an <link linkend="aliases">alias</link>
     for <function>current</function>.
    </simpara>
    <para>
     See also
     <function>end</function>, <function>next</function>,
     <function>prev</function>, and <function>reset</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.prev">
   <refnamediv>
    <refname>prev</refname>
    <refpurpose>Rewind the internal array pointer</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>prev</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     Returns the array element in the previous place that's pointed by
     the internal array pointer, or &false; if there are no more
     elements.
     <warning>
      <para>
       If the array contains empty elements then this function will
       return &false; for these elements as well.
       To properly traverse an array which may contain empty elements
       see the <function>each</function> function.
      </para>
     </warning>
    </para>
    <para>
     <function>prev</function> behaves just like
     <function>next</function>, except it rewinds the internal array
     pointer one place instead of advancing it.
    </para>
    <para>
     See also <function>current</function>, <function>end</function>,
     <function>next</function>, and <function>reset</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.range">
   <refnamediv>
    <refname>range</refname>
    <refpurpose>
     Create an array containing a range of elements
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>array</type><methodname>range</methodname>
      <methodparam><type>mixed</type><parameter>low</parameter></methodparam>
      <methodparam><type>mixed</type><parameter>high</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>range</function> returns an array of elements from
     <parameter>low</parameter> to <parameter>high</parameter>,
     inclusive.  If low > high, the sequence will be from high to low.
    </para>
    <example>
     <title><function>range</function> examples</title>
     <programlisting role="php">
<![CDATA[
foreach(range(0, 9) as $number) {
    echo $number;
}
foreach(range('a', 'z') as $letter) {
    echo $letter;
}
foreach(range('z', 'a') as $letter) {
    echo $letter;
}
]]>
     </programlisting>
    </example>
    <note>
     <para>
      Prior to version 4.1.0 the <function>range</function> function
      only generated incrementing integer arrays.  Support for
      character sequences and decrementing arrays was added in 4.1.0.
     </para>
     <example>
      <title>Simulating decrementing ranges and character sequences</title>
      <programlisting role="php">
<![CDATA[
# array_reverse can be used to flip the order of a range
foreach(array_reverse(range(0,9)) as $number) {
    echo $number;
}

# array_map() can be used to turn integers into characters using chr()
foreach(array_map('chr', range(ord('a'),ord('z'))) as $character) {
    echo $character;
}
]]>
      </programlisting>
     </example>
    </note>
    <para>
     See <function>shuffle</function> for another example of its use.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.reset">
   <refnamediv>
    <refname>reset</refname>
    <refpurpose>
     Set the internal pointer of an array to its first element
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>mixed</type><methodname>reset</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>reset</function> rewinds <parameter>array</parameter>'s
     internal pointer to the first element.
    </para>
    <para>
     <function>reset</function> returns the value of the first array
     element.
    </para>
    <para>
     See also <function>current</function>,
     <function>each</function>, <function>next</function>,
     and <function>prev</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.rsort">
   <refnamediv>
    <refname>rsort</refname>
    <refpurpose>Sort an array in reverse order</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>rsort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>sort_flags</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function sorts an array in reverse order (highest to lowest).
     <example>
      <title><function>rsort</function> example</title>
      <programlisting role="php">
<![CDATA[
$fruits = array ("lemon", "orange", "banana", "apple");
rsort ($fruits);
reset ($fruits);
while (list ($key, $val) = each ($fruits)) {
    echo "$key = $val\n";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
<![CDATA[
0 = orange
1 = lemon
2 = banana
3 = apple
]]>
     </screen>
    </para>
    <para>
     The fruits have been sorted in reverse alphabetical order.
    </para>
    <para>
     You may modify the behavior of the sort using the optional
     parameter <parameter>sort_flags</parameter>, for details
     see <function>sort</function>.
    </para>
    <para>
     See also <function>arsort</function>,
     <function>asort</function>, <function>ksort</function>,
     <function>sort</function>, and <function>usort</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.shuffle">
   <refnamediv>
    <refname>shuffle</refname>
    <refpurpose>Shuffle an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>shuffle</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function shuffles (randomizes the order of the elements in)
     an array. You must use <function>srand</function> to seed this
     function.
     <example>
      <title><function>shuffle</function> example</title>
      <programlisting role="php">
<![CDATA[
$numbers = range (1,20);
srand ((float)microtime()*1000000);
shuffle ($numbers);
while (list (, $number) = each ($numbers)) {
    echo "$number ";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     See also <function>arsort</function>, <function>asort</function>,
     <function>ksort</function>, <function>rsort</function>,
     <function>sort</function>, and <function>usort</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.sizeof">
   <refnamediv>
    <refname>sizeof</refname>
    <refpurpose>Get the number of elements in variable</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>sizeof</methodname>
      <methodparam><type>mixed</type><parameter>var</parameter></methodparam>
     </methodsynopsis>
    <para>
     The <function>sizeof</function> function is an
     <link linkend="aliases">alias</link> for <function>count</function>.
    </para>
    <para>
     See also <function>count</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.sort">
   <refnamediv>
    <refname>sort</refname>
    <refpurpose>Sort an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>sort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>sort_flags</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function sorts an array.  Elements will be arranged from
     lowest to highest when this function has completed.
     <example>
      <title><function>sort</function> example</title>
      <programlisting role="php">
<![CDATA[
<?php

$fruits = array ("lemon", "orange", "banana", "apple");
sort ($fruits);
reset ($fruits);
while (list ($key, $val) = each ($fruits)) {
    echo "fruits[".$key."] = ".$val."\n";
}

?>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
<![CDATA[
fruits[0] = apple
fruits[1] = banana
fruits[2] = lemon
fruits[3] = orange
]]>
     </screen>
    </para>
    <para>
     The fruits have been sorted in alphabetical order.
    </para>
    <para>
     The optional second parameter <parameter>sort_flags</parameter>
     may be used to modify the sorting behavior using these values:
    </para>
    <para>
     Sorting type flags:
     <itemizedlist>
      <listitem>
       <simpara>SORT_REGULAR - compare items normally</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_NUMERIC - compare items numerically</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_STRING - compare items as strings</simpara>
      </listitem>
     </itemizedlist>
    </para>
    <para>
     See also <function>arsort</function>,
     <function>asort</function>, <function>ksort</function>,
     <function>natsort</function>, <function>natcasesort</function>,
     <function>rsort</function>, <function>usort</function>,
     <function>array_multisort</function>, and
     <function>uksort</function>.
    </para>
    <note>
     <para>
      The second parameter was added in PHP 4.
     </para>
    </note>
   </refsect1>
  </refentry>

  <refentry id="function.uasort">
   <refnamediv>
    <refname>uasort</refname>
    <refpurpose>
     Sort an array with a user-defined comparison function and
     maintain index association
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>uasort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam><type>function</type><parameter>cmp_function</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function sorts an array such that array indices maintain
     their correlation with the array elements they are associated
     with.  This is used mainly when sorting associative arrays where
     the actual element order is significant.  The comparison function
     is user-defined.
    </para>
    <note>
     <para>
      Please see <function>usort</function> and
      <function>uksort</function> for examples of user-defined
      comparison functions.
     </para>
    </note>
    &note.func-callback;
    <para>
     See also <function>usort</function>, <function>uksort</function>,
     <function>sort</function>, <function>asort</function>,
     <function>arsort</function>, <function>ksort</function>,
     and <function>rsort</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.uksort">
   <refnamediv>
    <refname>uksort</refname>
    <refpurpose>
     Sort an array by keys using a user-defined comparison function
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>uksort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam><type>function</type><parameter>cmp_function</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function will sort the keys of an array using a
     user-supplied comparison function.  If the array you wish to sort
     needs to be sorted by some non-trivial criteria, you should use
     this function.
    </para>
    <example>
     <title><function>uksort</function> example</title>
     <programlisting role="php">
<![CDATA[
function cmp ($a, $b) {
    if ($a == $b) return 0;
    return ($a > $b) ? -1 : 1;
}

$a = array (4 => "four", 3 => "three", 20 => "twenty", 10 => "ten");

uksort ($a, "cmp");

while (list ($key, $value) = each ($a)) {
    echo "$key: $value\n";
}
]]>
     </programlisting>
    </example>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
<![CDATA[
20: twenty
10: ten
4: four
3: three
]]>
     </screen>
    </para>
    &note.func-callback;
    <para>
     See also <function>usort</function>, <function>uasort</function>,
     <function>sort</function>, <function>asort</function>,
     <function>arsort</function>, <function>ksort</function>,
     <function>natsort</function>, and <function>rsort</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.usort">
   <refnamediv>
    <refname>usort</refname>
    <refpurpose>
     Sort an array by values using a user-defined comparison function
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>usort</methodname>
      <methodparam><type>array</type><parameter>array</parameter></methodparam>
      <methodparam><type>string</type><parameter>cmp_function</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function will sort an array by its values using a
     user-supplied comparison function.  If the array you wish to sort
     needs to be sorted by some non-trivial criteria, you should use
     this function.
    </para>
    <para>
     The comparison function must return an integer less than, equal
     to, or greater than zero if the first argument is considered to
     be respectively less than, equal to, or greater than the
     second. If two members compare as equal, their order in the
     sorted array is undefined.
    </para>
    <para>
     <example>
      <title><function>usort</function> example</title>
      <programlisting role="php">
<![CDATA[
function cmp ($a, $b) {
    if ($a == $b) return 0;
    return ($a > $b) ? -1 : 1;
}

$a = array (3, 2, 5, 6, 1);

usort ($a, "cmp");

while (list ($key, $value) = each ($a)) {
    echo "$key: $value\n";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
<![CDATA[
0: 6
1: 5
2: 3
3: 2
4: 1
]]>
     </screen>
    </para>
    <note>
     <para>
      Obviously in this trivial case the <function>rsort</function>
      function would be more appropriate.
     </para>
    </note>
    <para>
     <example>
      <title>
       <function>usort</function> example using multi-dimensional array
      </title>
      <programlisting role="php">
<![CDATA[
function cmp ($a, $b) {
    return strcmp($a["fruit"], $b["fruit"]);
}

$fruits[0]["fruit"] = "lemons";
$fruits[1]["fruit"] = "apples";
$fruits[2]["fruit"] = "grapes";

usort($fruits, "cmp");

while (list ($key, $value) = each ($fruits)) {
    echo "\$fruits[$key]: " . $value["fruit"] . "\n";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     When sorting a multi-dimensional array, $a and $b contain
     references to the first index of the array.
    </para>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
<![CDATA[
$fruits[0]: apples
$fruits[1]: grapes
$fruits[2]: lemons
]]>
     </screen>
    </para>
    &note.func-callback;
    <para>
     <example>
      <title>
       <function>usort</function> example using a member function of an object
      </title>
      <programlisting role="php">
<![CDATA[
class TestObj {
    var $name;

    function TestObj($name)
    {
        $this->name = $name;
    }

    /* This is the static comparing function: */
    function cmp_obj($a, $b)
    {
        $al = strtolower($a->name);
        $bl = strtolower($b->name);
        if ($al == $bl) return 0;
        return ($al > $bl) ? +1 : -1;
    }
}

$a[] = new TestObj("c");
$a[] = new TestObj("b");
$a[] = new TestObj("d");

uasort($a, array ("TestObj", "cmp_obj"));

foreach ($a as $item) {
    print $item->name."\n";
}
]]>
      </programlisting>
     </example>
    </para>
    <para>
     This example would display:
    </para>
    <para>
     <screen>
b
c
d
     </screen>
    </para>
    <warning>
     <para>
      The underlying quicksort function in some C libraries (such as
      on Solaris systems) may cause PHP to crash if the comparison
      function does not return consistent values.
     </para>
    </warning>
    <para>
     See also <function>uasort</function>,
     <function>uksort</function>, <function>sort</function>,
     <function>asort</function>,
     <function>arsort</function>,<function>ksort</function>,
     <function>natsort</function>, and <function>rsort</function>.
    </para>
   </refsect1>
  </refentry>

 </reference>

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