php__silex__book/src/demo/Controllers/ErrorController.php

<?php

namespace demo\Controllers;

use Silex\Application;
use Symfony\Component\HttpFoundation\Response;

class ErrorController {

  public function errorBase(Application $app) {
    throw new \InvalidArgumentException('This route is always in error.');
  }

  public function errorHttp(Application $app) {
    $app->abort(Response::HTTP_TOO_MANY_REQUESTS);
  }
}