It seems a pretty common FAQ that the Route isn't recognized if the LuckyController.php doesn't start with the PHP header '<?php', and unfortunately that's the first code that any beginner in Symfony will try to write (copy/paste).

I'd suggest to add that header to the code inhttps://github.com/symfony/symfony-docs/blob/3.0/book/page_creation.rst#creating-a-page-route-and-controller

Hope this helps.