src/Application.php
public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = true)
    {
        if (!$this->booted) {
            $this->boot();
        }

        $request->attributes->set('app', $this);

        return $this->kernel->handle($request, $type, $catch);
    }
public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = true)
    {
        if (!$this->booted) {
            $this->boot();
        }

        $request->attributes->set('app', $this);

        return $this->kernel->handle($request, $type, $catch);
    }
Handles a Request to convert it to a Response.

@param Request $request A Request instance
@param int     $type    The type of the request
(one of HttpKernelInterface::MASTER_REQUEST or HttpKernelInterface::SUB_REQUEST)
@param bool    $catch   Whether to catch exceptions or not

@return Response A Response instance