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<refentry xml:id="function.array-diff-key" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>array_diff_key</refname>
  <refpurpose>Computes the difference of arrays using keys for comparison</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>array</type><methodname>array_diff_key</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>
   Compares the keys from <parameter>array1</parameter> against the keys
   from <parameter>array2</parameter> and returns the difference.
   This function is like <function>array_diff</function> except the
   comparison is done on the keys instead of the values.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>

    <varlistentry>
     <term><parameter>array1</parameter></term>
     <listitem>
      <para>
       The array to compare from
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><parameter>array2</parameter></term>
     <listitem>
      <para>
       An array to compare against
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><parameter>...</parameter></term>
     <listitem>
      <para>
       More 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>array1</parameter> that are not present in any of the other arrays.
  </para>
 </refsect1>

<!--
 <refsect1 role="errors">
  &reftitle.errors;
  &errors.no.unusual.errors;
 </refsect1>
-->

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>array_diff_key</function> example</title>
    <para>
     The two keys from the <literal>key =&gt; value</literal> pairs are
     considered equal only if
     <literal>(string) $key1 === (string) $key2 </literal>. In other words
     a strict type check is executed so the string representation must be
     the same.
    </para>
    <programlisting role="php">
<![CDATA[
<?php
$array1 = array('blue'  => 1, 'red'  => 2, 'green'  => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan'   => 8);

var_dump(array_diff_key($array1, $array2));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
array(2) {
  ["red"]=>
  int(2)
  ["purple"]=>
  int(4)
}
]]>
    </screen>
   </example>
  </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_key($array1[0], $array2[0]);</literal>.
   </para>
  </note>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>array_diff</function></member>
    <member><function>array_udiff</function></member>
    <member><function>array_diff_assoc</function></member>
    <member><function>array_diff_uassoc</function></member>
    <member><function>array_udiff_assoc</function></member>
    <member><function>array_udiff_uassoc</function></member>
    <member><function>array_diff_ukey</function></member>
    <member><function>array_intersect</function></member>
    <member><function>array_intersect_assoc</function></member>
    <member><function>array_intersect_uassoc</function></member>
    <member><function>array_intersect_key</function></member>
    <member><function>array_intersect_ukey</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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