Ogone\AbstractResponse::getParam PHP Method

    public function getParam($key)
    {
        if (method_exists($this, 'get' . $key)) {
            return $this->{'get' . $key}();
        }
        // always use uppercase
        $key = strtoupper($key);
        if (!array_key_exists($key, $this->parameters)) {
            throw new InvalidArgumentException('Parameter ' . $key . ' does not exist.');
        }
        return $this->parameters[$key];
    }