Queue::setLastItem

protected function setLastItem($item)
{
	if ($this->lastItem)
	{
		if (count($this->previousStack) >= 3)
		{
			array_shift($this->previousStack);
		}
		array_push($this->previousStack, $this->lastItem);
	}
	$this->lastItem = $item;

	return $this;
}