public function release($item)
	{
		// search the item in the used items array
		$k = array_search($item, $this->_inUseItems);
		if ( $k === FALSE )
			return;
			
		// remove it from the used items and adding it to the pool
		unset($this->_inUseItems[$k]);
		$this->_poolItems[] = $item;
	}