/**
  * @return null|string
  */
 protected function getRequestMethod()
 {
     $method = $_SERVER['REQUEST_METHOD'];
     if (!HttpConst::isMethod($method)) {
         return null;
     }
     return $method;
 }
 /**
  * @param  int $code
  * @return AbstractModeHandler this
  */
 protected function error($code)
 {
     if (!HttpConst::isStatus($code)) {
         throw new RuntimeException('unknown HTTP-Status Code `' . $code . '`');
     }
     http_response_code($code);
     # pipe to URL
     if (isset($this->settings['err' . $code . '-pipe'])) {
         $target = new MAPUrl($this->settings['err' . $code . '-pipe'], $this->config);
         if ($target->get() === $this->request->get()) {
             Logger::error('endless pipe-loop (status: `' . $code . '`) - interrupted with HTTP-Status `508`');
             return $this->error(508);
         }
         $this->setLocation(new Url($this->settings['err' . $code . '-pipe']));
         return $this;
     }
     # default error output
     if (defined('peer\\http\\HttpConst::STATUS_' . $code)) {
         $message = constant('peer\\http\\HttpConst::STATUS_' . $code);
     } else {
         $message = 'N/A';
     }
     $this->setContentType('text/plain');
     echo '[' . $code . '] ' . $message;
     return $this;
 }