index.php

#!/usr/bin/php
<?php

require_once __DIR__ . '/PartialIterator.php';

$array = array(
    '1element',
    '2element',
    '3element',
    '4element',
    '5element',
    '6element',
    '7element',
);

$obj = new \ArrayObject($array);
$it = $obj->getIterator();

$partial = new PartialIterator($it, 3);
var_dump('1');
foreach ($partial as $iterator)
{
    var_dump($iterator);
}

$partial = new PartialIterator($it, 3);
var_dump('2');
foreach ($partial as $iterator)
{
    var_dump($iterator);
}

PartialIterator.php

<?php

/**
 * Итератор возвращает набор значений начального итератора
 */
class PartialIterator implements \Iterator
{
    /**
     * @var int Текущая позиция итератора
     */
    private $position = 0;

    /**
     * @var \Iterator Начальный итератор
     */
    private $iterator;

    /**
     * @var int Максимальное количество возвращаемых значений
     */
    private $maxItems;

    /**
     * @var bool Флаг вызова rewind()
     */
    private $isRewindAlready = false;

    /**
     * @param \Iterator $iterator Начальный итератор
     * @param int       $maxItems Максимальное количество возвращаемых значений
     */
    public function __construct(\Iterator $iterator, $maxItems = 3)
    {
        $this->iterator = $iterator;
        $this->maxItems = $maxItems;
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Return the current element
     * @link http://php.net/manual/en/iterator.current.php
     * @return mixed Can return any type.
     */
    public function current()
    {
        return $this->iterator->current();
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Move forward to next element
     * @link http://php.net/manual/en/iterator.next.php
     * @return void Any returned value is ignored.
     */
    public function next()
    {
        $this->iterator->next();
        ++$this->position;
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Return the key of the current element
     * @link http://php.net/manual/en/iterator.key.php
     * @return mixed scalar on success, or null on failure.
     */
    public function key()
    {
        return $this->position;
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Checks if current position is valid
     * @link http://php.net/manual/en/iterator.valid.php
     * @return boolean The return value will be casted to boolean and then evaluated.
     * Returns true on success or false on failure.
     */
    public function valid()
    {
        return $this->position < $this->maxItems && $this->iterator->valid();
    }

    /**
     * (PHP 5 &gt;= 5.0.0)<br/>
     * Rewind the Iterator to the first element
     * @link http://php.net/manual/en/iterator.rewind.php
     * @throws LogicException
     * @return void Any returned value is ignored.
     */
    public function rewind()
    {
        if ($this->isRewindAlready)
        {
            throw new \LogicException("You can't call rewind twice");
        }

        $this->isRewindAlready = true;
    }
}