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<refentry xml:id="function.iterator-apply" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>iterator_apply</refname>
  <refpurpose>Call a function for every element in an iterator</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>int</type><methodname>iterator_apply</methodname>
   <methodparam><type>Traversable</type><parameter>iterator</parameter></methodparam>
   <methodparam><type>callable</type><parameter>callback</parameter></methodparam>
   <methodparam choice="opt"><type class="union"><type>array</type><type>null</type></type><parameter>args</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   Calls a function for every element in an iterator.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>iterator</parameter></term>
     <listitem>
      <para>
       The iterator object to iterate over.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>callback</parameter></term>
     <listitem>
      <para>
       The callback function to call on every element.
       This function only receives the given <parameter>args</parameter>, so it
       is nullary by default. If <literal>count($args) === 3</literal>, for
       instance, the callback function is ternary.
       <note>
        <simpara>
         The function must return &true; in order to
         continue iterating over the <parameter>iterator</parameter>.
        </simpara>
       </note>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>args</parameter></term>
     <listitem>
      <para>
       An <type>array</type> of arguments; each element of
       <parameter>args</parameter> is passed to the callback
       <parameter>callback</parameter> as separate argument.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the iteration count.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>iterator_apply</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
function print_caps(Iterator $iterator) {
    echo strtoupper($iterator->current()) . "\n";
    return TRUE;
}

$it = new ArrayIterator(array("Apples", "Bananas", "Cherries"));
iterator_apply($it, "print_caps", array($it));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
APPLES
BANANAS
CHERRIES
]]>
    </screen>
   </example>
  </para>
 </refsect1>

<!--
 <refsect1 role="errors">
  &reftitle.errors;
  <para>
   When does this function issue E_* level errors, and/or throw exceptions.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>iterator_apply</function> example</title>
    <para>
     Any text that describes the purpose of the example, or what
     goes on in the example should be here.
    </para>
    <programlisting role="php">
<![CDATA[
<?php

/* ... */

?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
...
]]>
    </screen>
   </example>
  </para>
 </refsect1>
-->

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>array_walk</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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