php-doc-en/reference/array/functions/uksort.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision$ -->
<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>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>
 </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>cmp_function</parameter></term>
     <listitem>
      <para>
       The callback comparison 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>
     </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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