doc-en/language/predefined/iterator.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<reference xml:id="class.iterator" role="class" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude">

 <title>The Iterator interface</title>
 <titleabbrev>Iterator</titleabbrev>

 <partintro>

<!-- {{{ Iterator intro -->
  <section xml:id="iterator.intro">
   &reftitle.intro;
   <para>
    Interface for external iterators or objects that can be iterated
    themselves internally.
   </para>
  </section>
<!-- }}} -->

  <section xml:id="iterator.synopsis">
   &reftitle.interfacesynopsis;

<!-- {{{ Synopsis -->
   <classsynopsis class="interface">
    <oointerface>
     <interfacename>Iterator</interfacename>
    </oointerface>

    <oointerface>
     <modifier>extends</modifier>
     <interfacename>Traversable</interfacename>
    </oointerface>

    <classsynopsisinfo role="comment">&Methods;</classsynopsisinfo>
    <xi:include xpointer="xmlns(db=http://docbook.org/ns/docbook) xpointer(id('class.iterator')/db:refentry/db:refsect1[@role='description']/descendant::db:methodsynopsis[@role='Iterator'])">
     <xi:fallback/>
    </xi:include>
   </classsynopsis>
<!-- }}} -->

  </section>
  
  <section xml:id="iterator.iterators">
   <title>Predefined iterators</title>
   <para>
    PHP already provides a number of iterators for many day to day tasks.
    See <link linkend="spl.iterators">SPL iterators</link> for a list.
   </para>
  </section>

  <section xml:id="iterator.examples">
   &reftitle.examples;
   <example xml:id="iterator.example.basic"><!-- {{{ -->
    <title>Basic usage</title>
    <para>
     This example demonstrates in which order methods are called when
     using &foreach; with an iterator.
    </para>
    <programlisting role="php">
<![CDATA[
<?php
class myIterator implements Iterator {
    private $position = 0;
    private $array = array(
        "firstelement",
        "secondelement",
        "lastelement",
    );  

    public function __construct() {
        $this->position = 0;
    }

    public function rewind(): void {
        var_dump(__METHOD__);
        $this->position = 0;
    }

    #[\ReturnTypeWillChange]
    public function current() {
        var_dump(__METHOD__);
        return $this->array[$this->position];
    }

    #[\ReturnTypeWillChange]
    public function key() {
        var_dump(__METHOD__);
        return $this->position;
    }

    public function next(): void {
        var_dump(__METHOD__);
        ++$this->position;
    }

    public function valid(): bool {
        var_dump(__METHOD__);
        return isset($this->array[$this->position]);
    }
}

$it = new myIterator;

foreach($it as $key => $value) {
    var_dump($key, $value);
    echo "\n";
}
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(0)
string(12) "firstelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(1)
string(13) "secondelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(2)
string(11) "lastelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
]]>
    </screen>
   </example><!-- }}} -->
  </section>

  <section xml:id="iterator.seealso">
  &reftitle.seealso;
   <para>See also <link linkend="language.oop5.iterations">object iteration</link>.</para>
  </section>

 </partintro>

 &language.predefined.iterator.current;
 &language.predefined.iterator.key;
 &language.predefined.iterator.next;
 &language.predefined.iterator.rewind;
 &language.predefined.iterator.valid;

</reference>
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