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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.17 $ -->
<!-- splitted from ./en/functions/array.xml, last change in rev 1.62 -->
<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>callback</type><parameter>callback</parameter></methodparam>
</methodsynopsis>
<para>
<function>array_filter</function> iterates over each value in
the <parameter>input</parameter> array passing them to the
<parameter>callback</parameter> function. If the <parameter>
callback</parameter> function returns true, the current
value from <parameter>input</parameter> is returned into the
result array. Array keys are preserved.
</para>
<para>
<example>
<title><function>array_filter</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
function odd($var)
{
return($var & 1);
}
function even($var)
{
return(!($var & 1));
}
$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>
&example.outputs;
<screen role="php">
<![CDATA[
Odd :
Array
(
[a] => 1
[c] => 3
[e] => 5
)
Even:
Array
(
[0] => 6
[2] => 8
[4] => 10
[6] => 12
)
]]>
</screen>
</example>
</para>
<para>
Users may not change the array itself from the callback
function. e.g. Add/delete an element, unset the array that
<function>array_filter</function> is applied to. If the array
is changed, the behavior of this function is undefined.
</para>
<para>
If the <parameter>callback</parameter> function is not supplied,
<function>array_filter</function> will remove all the entries of
<parameter>input</parameter> that are equal to &false;. See <link
linkend="language.types.boolean.casting">converting to boolean</link>
for more information.
</para>
<para>
<example>
<title><function>array_filter</function> without
<parameter>callback</parameter></title>
<programlisting role="php">
<![CDATA[
<?php
$entry = array(
0 => 'foo',
1 => false,
2 => -1,
3 => null,
4 => ''
);
print_r(array_filter($entry));
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
Array
(
[0] => foo
[2] => -1
)
]]>
</screen>
</example>
</para>
<para>
See also <function>array_map</function>,
<function>array_reduce</function>, and <function>array_walk</function>.
</para>
</refsect1>
</refentry>
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