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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.array-diff" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>array_diff</refname>
<refpurpose>Computes the difference of arrays</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>array</type><methodname>array_diff</methodname>
<methodparam><type>array</type><parameter>array</parameter></methodparam>
<methodparam rep="repeat"><type>array</type><parameter>arrays</parameter></methodparam>
</methodsynopsis>
<para>
Compares <parameter>array</parameter> against one or more other arrays and
returns the values in <parameter>array</parameter> that are not present in
any of the other arrays.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>array</parameter></term>
<listitem>
<para>
The array to compare from
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>arrays</parameter></term>
<listitem>
<para>
Arrays to compare against
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns an <type>array</type> containing all the entries from
<parameter>array</parameter> that are not present in any of the other arrays.
Keys in the <parameter>array</parameter> array are preserved.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
&array.changelog.require-only-one;
</tbody>
</tgroup>
</informaltable>
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>array_diff</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);
print_r($result);
?>
]]>
</programlisting>
<para>
Multiple occurrences in <varname>$array1</varname> are all
treated the same way. This will output :
</para>
<screen>
<![CDATA[
Array
(
[1] => blue
)
]]>
</screen>
</example>
</para>
<para>
Two elements are considered equal if and only if
<literal>(string) $elem1 === (string) $elem2</literal>. That is,
when the <link linkend="language.types.string.casting">string representation</link> is the same.
</para>
<para>
<example>
<title><function>array_diff</function> example with non-matching types</title>
<programlisting role="php">
<![CDATA[
<?php
// This will generate a Notice that an array cannot be cast to a string.
$source = [1, 2, 3, 4];
$filter = [3, 4, [5], 6];
$result = array_diff($source, $filter);
// Whereas this is fine, since the objects can cast to a string.
class S {
private $v;
public function __construct(string $v) {
$this->v = $v;
}
public function __toString() {
return $this->v;
}
}
$source = [new S('a'), new S('b'), new S('c')];
$filter = [new S('b'), new S('c'), new S('d')];
$result = array_diff($source, $filter);
// $result now contains one instance of S('a');
var_dump($result);
?>
]]>
</programlisting>
</example>
</para>
<para>
To use an alternate comparison function, see <function>array_udiff</function>.
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
<note>
<para>
This function only checks one dimension of a n-dimensional
array. Of course you can check deeper dimensions by using
<literal>array_diff($array1[0], $array2[0]);</literal>.
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>array_diff_assoc</function></member>
<member><function>array_udiff</function></member>
<member><function>array_intersect</function></member>
<member><function>array_intersect_assoc</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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