public function mapParams(array $map, $params = null)
    {
        if (!isset($params)) {
            $params = $this->params;
        }

        $mapped = array();

        foreach ($params as $key => $value) {
            if (isset($map[$key]) && is_string($map[$key])) {
                gplcart_array_set($mapped, $map[$key], $value);
            }
        }

        return $mapped;
    }