protected function determineProtocolVersion()
    {
        $params = $this->getServerParams();
        
        if (isset($params['SERVER_PROTOCOL'])) {
            list($protocol, $version) = explode('/', $params['SERVER_PROTOCOL']) + [1 => null];
        }
        
        return isset($protocol) && $protocol === 'HTTP' ? $version : "1.1";
    }