<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.uksort" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>uksort</refname>
  <refpurpose>Sort an array by keys using a user-defined comparison function</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>uksort</methodname>
   <methodparam><type>array</type><parameter role="reference">array</parameter></methodparam>
   <methodparam><type>callable</type><parameter>key_compare_func</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>uksort</function> will sort the keys of an array using a
   user-supplied comparison function.  If the array you wish to sort
   needs to be sorted by some non-trivial criteria, you should use
   this function.
  </para>
  &note.sort-unstable;
 </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>key_compare_func</parameter></term>
     <listitem>
      <para>
       &return.callbacksort;
      </para>
      &callback.cmp;
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>uksort</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
function cmp($a, $b)
{
    $a = preg_replace('@^(a|an|the) @', '', $a);
    $b = preg_replace('@^(a|an|the) @', '', $b);
    return strcasecmp($a, $b);
}

$a = array("John" => 1, "the Earth" => 2, "an apple" => 3, "a banana" => 4);

uksort($a, "cmp");

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
an apple: 3
a banana: 4
the Earth: 2
John: 1
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>usort</function></member>
    <member>&seealso.array.sorting;</member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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