php__silex__book/src/demo/Controllers/FeedbackController.php

<?php

namespace demo\Controllers;


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

class FeedbackController {

  public function feedbackAction(Application $app, Request $request) {
    $message = $request->get('message');
    mail($app['app.mail_to'], '[YourSite] Feedback', $message);
    return new Response('Thank you for your feedback!', Response::HTTP_CREATED);
  }
}