Symfony\Component\HttpKernel\HttpKernel::handle PHP Method

    public function handle(Request $request, $type = HttpKernelInterface::MASTER_REQUEST, $catch = true)
    {
        $request->headers->set('X-Php-Ob-Level', ob_get_level());

        try {
            return $this->handleRaw($request, $type);
        } catch (\Exception $e) {
            if ($e instanceof RequestExceptionInterface) {
                $e = new BadRequestHttpException($e->getMessage(), $e);
            }
            if (false === $catch) {
                $this->finishRequest($request, $type);

                throw $e;
            }

            return $this->handleException($e, $request, $type);
        }
    }

 public function run()
 {
     $this->response = $this->kernel->handle($this->request);
     $this->response->send();
     $this->kernel->terminate($this->request, $this->response);
     return $this;
 }