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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<refentry xml:id="function.array-walk" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>array_walk</refname>
<refpurpose>Apply a user function to every member of an array</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<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>
Applies the user-defined function <parameter>funcname</parameter> to each
element of the <parameter>array</parameter> array.
</simpara>
<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.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>array</parameter></term>
<listitem>
<para>
The input array.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>funcname</parameter></term>
<listitem>
<para>
Typically, <parameter>funcname</parameter> takes on two parameters.
The <parameter>array</parameter> parameter's value being the first, and
the key/index second.
</para>
<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>
<para>
Users may not change the <parameter>array</parameter> 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>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>userdata</parameter></term>
<listitem>
<para>
If the optional <parameter>userdata</parameter> parameter is supplied,
it will be passed as the third parameter to the callback
<parameter>funcname</parameter>.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
&return.success;
</para>
</refsect1>
<refsect1 role="errors">
&reftitle.errors;
<para>
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>.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<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>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>array_walk_recursive</function></member>
<member><function>iterator_apply</function></member>
<member><function>create_function</function></member>
<member><function>list</function></member>
<member><function>each</function></member>
<member><function>call_user_func_array</function></member>
<member><function>array_map</function></member>
<member>&seealso.callback;</member>
<member>&foreach;</member>
</simplelist>
</para>
</refsect1>
</refentry>
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