I start the tutorial (as newbie) and everythings works fine till:
http://symfony.com/doc/current/book/page_creation.html#creating-a-page-route-and-controller at step
Try this URL:
http://[Server-IP]:8000/app_dev.php/en/lucky/number
There's a bug in the Symfony Book: they forgot the demo app support i18n.
Just add the "/en" parameter before the routing ones.
I know this question it's closed but I hope my answer can help others that are still facing this problem.