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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.24 $ -->
<!-- splitted from ./en/functions/array.xml, last change in rev 1.2 -->
<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>bool</type><methodname>array_walk</methodname>
<methodparam><type>array</type><parameter role="reference">array</parameter></methodparam>
<methodparam><type>callback</type><parameter>funcname</parameter></methodparam>
<methodparam choice="opt"><type>mixed</type><parameter>userdata</parameter></methodparam>
</methodsynopsis>
<simpara>
&return.success;
</simpara>
<simpara>
Applies the user-defined function <parameter>funcname</parameter> to each
element of the <parameter>array</parameter> array. Typically,
<parameter>funcname</parameter> takes on two parameters.
The <parameter>array</parameter> parameter's value being the first, and
the key/index second. If the optional <parameter>userdata</parameter>
parameter is supplied, it will be passed as the third parameter to
the callback <parameter>funcname</parameter>.
</simpara>
<simpara>
If function <parameter>funcname</parameter> requires more parameters than
given to it, an error of level <link linkend="errorfunc.constants">
E_WARNING</link> will be generated each time <function>array_walk</function>
calls <parameter>funcname</parameter>. These warnings may be suppressed by
prepending the PHP error operator
<link linkend="language.operators.errorcontrol">@</link> to the
<function>array_walk</function> call, or by using
<function>error_reporting</function>.
</simpara>
<note>
<para>
If <parameter>funcname</parameter> needs to be working with the
actual values of the array, specify the first parameter of
<parameter>funcname</parameter> as a
<link linkend="language.references">reference</link>. Then,
any changes made to those elements will be made in the
original array itself.
</para>
</note>
<note>
<para>
Passing the key and userdata to <parameter>funcname</parameter> was
added in 4.0.0
</para>
</note>
<para>
<function>array_walk</function> is not affected by the internal
array pointer of <parameter>array</parameter>. <function>
array_walk</function> will walk through the entire array
regardless of pointer position. To reset the pointer, use
<function>reset</function>. In PHP 3,
<function>array_walk</function> resets the pointer.
</para>
<para>
Users may not change the array itself from the callback
function. e.g. Add/delete elements, unset elements, etc. If
the array that <function>array_walk</function> is applied to
is changed, the behavior of this function is undefined, and
unpredictable.
</para>
<para>
<example>
<title><function>array_walk</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");
function test_alter(&$item1, $key, $prefix)
{
$item1 = "$prefix: $item1";
}
function test_print($item2, $key)
{
echo "$key. $item2<br />\n";
}
echo "Before ...:\n";
array_walk($fruits, 'test_print');
array_walk($fruits, 'test_alter', 'fruit');
echo "... and after:\n";
array_walk($fruits, 'test_print');
?>
]]>
</programlisting>
&example.outputs;
<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>
</example>
</para>
<simpara>
See also <function>array_walk_recursive</function>,
<function>create_function</function>,
<function>list</function>,
<link linkend="control-structures.foreach">foreach</link>,
<function>each</function>,
<function>call_user_func_array</function>, and
<function>array_map</function>, and
&seealso.callback;.
</simpara>
</refsect1>
</refentry>
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