Neos\Flow\Http\Response::renderHeaders PHP Method

    public function renderHeaders()
    {
        $preparedHeaders = [];
        $statusHeader = rtrim($this->getStatusLine(), "\r\n");
        $preparedHeaders[] = $statusHeader;
        foreach ($this->headers->getAll() as $name => $values) {
            foreach ($values as $value) {
                $preparedHeaders[] = $name . ': ' . $value;
            }
        }
        return $preparedHeaders;
    }

 /**
  * Just return the processed value
  *
  * @return mixed
  */
 public function evaluate()
 {
     $httpResponse = new Response();
     $httpResponse->setStatus($this->getStatusCode());
     $httpResponse->setHeaders(new Headers());
     foreach ($this->getHeaders() as $name => $value) {
         $httpResponse->setHeader($name, $value);
     }
     return implode("\r\n", $httpResponse->renderHeaders()) . "\r\n\r\n";
 }