Symfony3 (and some versions of Symfony2) come with a new directory structure.
This updated version of Symfony.gitignore supports this new directory structure
as well as the old one.
Quoting from http://symfony.com/legacy
The symfony 1.x branch of the framework started in 2005 and the latest stable
version and long term support release is symfony 1.4. As of November 2012,
symfony 1.x is not maintained anymore and you are encouraged to have a look
at Symfony2 for any new projects.