ArrayIterator::rewind

<?php
$arrayobject = new ArrayObject();

$arrayobject[] = 'zero';
$arrayobject[] = 'one';
$arrayobject[] = 'two';

$iterator = $arrayobject->getIterator();

$iterator->next();
echo $iterator->key(); //1

$iterator->rewind(); //最初に巻き戻す
echo $iterator->key(); //0
?>