public function setParam($param, $value = null)
    {
        if (is_string($param)) {
            $this->_params[$param] = $value;

            return $this;
        }

        if (is_array($param)) {
            foreach ($param as $key => $value) {
                $this->_params[$key] = $value;
            }
        }

        return $this;
    }