<?xml version="1.0" encoding="iso-8859-1"?>
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  <refentry id="function.uksort">
   <refnamediv>
    <refname>uksort</refname>
    <refpurpose>
     Sort an array by keys using a user-defined comparison function
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>bool</type><methodname>uksort</methodname>
      <methodparam><type>array</type><parameter role="reference">array</parameter></methodparam>
      <methodparam><type>callback</type><parameter>cmp_function</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>
    <para>
     Function <parameter>cmp_function</parameter> should accept two
     parameters which will be filled by pairs of <parameter>array</parameter> keys.
     The comparison function must return an integer less than, equal
     to, or greater than zero if the first argument is considered to
     be respectively less than, equal to, or greater than the
     second.
    </para>
    <para>
     &return.success;
    </para>
    <para>
     <example>
      <title><function>uksort</function> example</title>
      <programlisting role="php">
<![CDATA[
<?php
function cmp($a, $b) 
{
    if ($a == $b) {
        return 0;
    }
    return ($a > $b) ? -1 : 1;
}

$a = array(4 => "four", 3 => "three", 20 => "twenty", 10 => "ten");

uksort($a, "cmp");

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}
?>
]]>
      </programlisting>
      &example.outputs;
      <screen>
<![CDATA[
20: twenty
10: ten
4: four
3: three
]]>
      </screen>
     </example>
    </para>
    <para>
     See also <function>usort</function>, <function>uasort</function>,
     <function>sort</function>, <function>asort</function>,
     <function>arsort</function>, <function>ksort</function>,
     <function>natsort</function>, and <function>rsort</function>.
    </para>
   </refsect1>
  </refentry>

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