archived-doc-zh/reference/array/functions/array-reduce.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- $Author$ -->
<!-- EN-Revision: 31cacb6f262f455c616094cfe6d09bc0d1df2748 Maintainer: daijie Status: ready -->
<refentry xml:id="function.array-reduce" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>array_reduce</refname>
  <refpurpose>用回调函数迭代地将数组简化为单一的值</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>mixed</type><methodname>array_reduce</methodname>
   <methodparam><type>array</type><parameter>array</parameter></methodparam>
   <methodparam><type>callable</type><parameter>callback</parameter></methodparam>
   <methodparam choice="opt"><type>mixed</type><parameter>initial</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   <function>array_reduce</function> 将回调函数
   <parameter>callback</parameter> 迭代地作用到
   <parameter>array</parameter> 数组中的每一个单元中，从而将数组简化为单一的值。
     </para>
 </refsect1>
  <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>array</parameter></term>
     <listitem>
      <para>
       输入的 array。
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>callback</parameter></term>
     <listitem>
      <methodsynopsis>
       <type>mixed</type><methodname><replaceable>callback</replaceable></methodname>
       <methodparam><type>mixed</type><parameter>carry</parameter></methodparam>
       <methodparam><type>mixed</type><parameter>item</parameter></methodparam>
      </methodsynopsis>
    <variablelist>
    <varlistentry>
     <term><parameter>carry</parameter></term>
     <listitem>
      <para>
        携带上次迭代的返回值；
       如果本次迭代是第一次，那么这个值是 <parameter>initial</parameter>。
      </para>
     </listitem>
    </varlistentry>
     <varlistentry>
        <term><parameter>item</parameter></term>
        <listitem>
         <para>
           携带了本次迭代的值。
         </para>
        </listitem>
       </varlistentry>
   </variablelist>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>initial</parameter></term>
     <listitem>
      <para>
       如果指定了可选参数
   <parameter>initial</parameter>，该参数将用作处理开始时的初始值，如果数组为空，则会作为最终结果返回。
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   返回结果值。
  </para>
  <para>
   如果数组为空，并且没有指定
   <parameter>initial</parameter> 参数，<function>array_reduce</function> 返回 &null;。
  </para>
 </refsect1>


 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     &array.changelog.by-ref;
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>array_reduce</function> 例子</title>
    <programlisting role="php">
<![CDATA[
<?php
function sum($carry, $item)
{
    $carry += $item;
    return $carry;
}

function product($carry, $item)
{
    $carry *= $item;
    return $carry;
}

$a = array(1, 2, 3, 4, 5);
$x = array();

var_dump(array_reduce($a, "sum")); // int(15)
var_dump(array_reduce($a, "product", 10)); // int(1200), 因为：10*1*2*3*4*5
var_dump(array_reduce($x, "sum", "No data to reduce")); // string(17) "No data to reduce"
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
  <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>array_filter</function></member>
    <member><function>array_map</function></member>
    <member><function>array_unique</function></member>
    <member><function>array_count_values</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->