This application is written in [Silex] (http://silex-project.org/) to show how to use the FormExtension
I use the [Symfony Forms] (http://symfony.com/doc/2.0/book/forms.html) documentation and read the [Silex Extensions] (https://github.com/igorw/Silex/tree/master/src/Silex/Extension) source code to understand how to implement it.
All other source code needed are added with
git add submodule
git submodule update
I will update this app with the ValidationExtension when it works for me.
Enjoy !