public function getItem($sProductId, $aSelList, $aPersParams = null)
    {
        // loading basket item list
        $aItems = $this->getItems();
        $sItemKey = $this->_getItemKey($sProductId, $aSelList, $aPersParams);
        $oItem = null;
        // returning existing item
        if (isset($aItems[$sProductId])) {
            $oItem = $aItems[$sProductId];
        } elseif (isset($aItems[$sItemKey])) {
            $oItem = $aItems[$sItemKey];
        } else {
            $oItem = $this->_createItem($sProductId, $aSelList, $aPersParams);
        }

        return $oItem;
    }