archived-doc-pt-br/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>Reduz um array para um único valor através de um processo iterativo via callback</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> aplica iterativamente a função
   <parameter>callback</parameter> aos elementos de
   <parameter>array</parameter>, de forma a reduzir o array a
   um único valor.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>array</parameter></term>
     <listitem>
      <para>
       O array de entrada.
      </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>
          Informa o valor da iteração anterior. No caso da
          primeira iteração ele terá o valor de
          <parameter>initial</parameter>.
         </para>
        </listitem>
       </varlistentry>
       <varlistentry>
        <term><parameter>item</parameter></term>
        <listitem>
         <para>
          Mantém o valor da iteração atual.
         </para>
        </listitem>
       </varlistentry>
      </variablelist>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>initial</parameter></term>
     <listitem>
      <para>
       Se o argumento opcional <parameter>initial</parameter>
       for passado, ele será utilizado no início do processo, ou como
       um resultado final se o array estiver vazio.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Retorna o valor resultante.
  </para>
  <para>
   Se a array estiver vazio e <parameter>initial</parameter> não for passado,
   <function>array_reduce</function> retornará &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>Exemplo de <function>array_reduce</function></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), because: 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>

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