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

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  <refentry id="function.array-multisort">
   <refnamediv>
    <refname>array_multisort</refname>
    <refpurpose>Sort multiple or multi-dimensional arrays</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>bool</type><methodname>array_multisort</methodname>
      <methodparam><type>array</type><parameter>ar1</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>arg</parameter></methodparam>
      <methodparam choice="opt"><type>mixed</type><parameter>...</parameter></methodparam>
      <methodparam choice="opt"><type>array</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>array_multisort</function> can be used to sort several
     arrays at once or a multi-dimensional array according by one of
     more dimensions. It maintains key association when sorting.
    </para>
    <para>
     The input arrays are treated as columns of a table to be sorted
     by rows - this resembles the functionality of SQL ORDER BY
     clause. The first array is the primary one to sort by. The rows
     (values) in that array that compare the same are sorted by the
     next input array, and so on.
    </para>
    <para>
     The argument structure of this function is a bit unusual, but
     flexible. The very first argument has to be an
     array. Subsequently, each argument can be either an array or a
     sorting flag from the following lists.
    </para>
    <para>
     Sorting order flags:
     <itemizedlist>
      <listitem>
       <simpara>SORT_ASC - sort in ascending order</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_DESC - sort in descending order</simpara>
      </listitem>
     </itemizedlist>
    </para>
    <para>
     Sorting type flags:
     <itemizedlist>
      <listitem>
       <simpara>SORT_REGULAR - compare items normally</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_NUMERIC - compare items numerically</simpara>
      </listitem>
      <listitem>
       <simpara>SORT_STRING - compare items as strings</simpara>
      </listitem>
     </itemizedlist>
    </para>
    <para>
     No two sorting flags of the same type can be specified after each
     array. The sorting flags specified after an array argument apply
     only to that array - they are reset to default SORT_ASC and
     SORT_REGULAR before each new array argument.
    </para>
    <para>
     &return.success;
    </para>
    <para>
     <example>
      <title>Sorting multiple arrays</title>
      <programlisting role="php">
<![CDATA[
$ar1 = array ("10", 100, 100, "a");
$ar2 = array (1, 3, "2", 1);
array_multisort ($ar1, $ar2);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     In this example, after sorting, the first array will contain 10,
     "a", 100, 100. The second array will contain 1, 1, "2", 3. The
     entries in the second array corresponding to the identical
     entries in the first array (100 and 100) were sorted as well.
    </para>
    <para>
     <example>
      <title>Sorting multi-dimensional array</title>
      <programlisting role="php">
<![CDATA[
$ar = array (array ("10", 100, 100, "a"), array (1, 3, "2", 1));
array_multisort ($ar[0], SORT_ASC, SORT_STRING,
                 $ar[1], SORT_NUMERIC, SORT_DESC);
]]>
      </programlisting>
     </example>
    </para>
    <para>
     In this example, after sorting, the first array will contain 10,
     100, 100, "a" (it was sorted as strings in ascending order), and
     the second one will contain 1, 3, "2", 1 (sorted as numbers, in
     descending order).
    </para>
   </refsect1>
  </refentry>

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