protected function _changeBasketItemKey($sOldKey, $sNewKey, $value = null)
    {
        reset($this->_aBasketContents);
        $iOldKeyPlace = 0;
        while (key($this->_aBasketContents) != $sOldKey && next($this->_aBasketContents)) {
            ++$iOldKeyPlace;
        }
        $aNewCopy = array_merge(
            array_slice($this->_aBasketContents, 0, $iOldKeyPlace, true),
            [$sNewKey => $value],
            array_slice($this->_aBasketContents, $iOldKeyPlace + 1, count($this->_aBasketContents) - $iOldKeyPlace, true)
        );
        $this->_aBasketContents = $aNewCopy;
    }