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

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<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>input</parameter></methodparam>
   <methodparam><type>callable</type><parameter>function</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>function</parameter> 迭代地作用到
   <parameter>input</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>input</parameter></term>
     <listitem>
      <para>
       The input array.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>function</parameter></term>
     <listitem>
      <para>
       The callback function.
      </para>
      <methodsynopsis>
       <type>mixed</type><methodname><replaceable>callback</replaceable></methodname>
       <methodparam><type>mixed</type><parameter role="reference">result</parameter></methodparam>
       <methodparam><type>mixed</type><parameter>item</parameter></methodparam>
      </methodsynopsis>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>initial</parameter></term>
     <listitem>
      <para>
       如果指定了可选参数
   <parameter>initial</parameter>，该参数将被当成是数组中的第一个值来处理，或者如果数组为空的话就作为最终返回值。
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   返回结果值。
  </para>
  <para>
   <parameter>initial</parameter> 参数，<function>array_reduce</function> 返回 &null;。
  </para>
 </refsect1>
  <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>5.3.0</entry>
       <entry>
        Changed <parameter>initial</parameter> to allow <type>mixed</type>, previously <type>integer</type>.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>array_reduce</function> 例子</title>
    <programlisting role="php">
<![CDATA[
<?php
function rsum($v, $w)
{
    $v += $w;
    return $v;
}

function rmul($v, $w)
{
    $v *= $w;
    return $v;
}

$a = array(1, 2, 3, 4, 5);
$x = array();
$b = array_reduce($a, "rsum");
$c = array_reduce($a, "rmul", 10);
$d = array_reduce($x, "rsum", "No data to reduce");
?>
]]>
    </programlisting>
    <para>
     这将使 <varname>$b</varname> 的值为
   <literal>15</literal>，<varname>$c</varname> 的值为
   <literal>1200</literal>（= 10*1*2*3*4*5），以及
   <varname>$d</varname> 的值为 <literal>1</literal>。
    </para>
   </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>

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