In this final post of his series about building a framework on Symfony2 components, Fabien Potencier focuses again on flexibility - allowing you to have more than one front controller with different configurations thanks to dependency injections.

Does it means that we have to make a choice between flexibility, customization, ease of testing and not having to copy and paste the same code into each application front controller? As you might expect, there is a solution. We can solve all these issues and some more by using the Symfony2 dependency injection container.

The Symfony2 DIC (DependencyInjection) allows you to create a container with the objects and settings that you want and inject that into the main "Framework" class for its use. He registers most of the components he's added over the series like the UrlMatcher, RouterListener, ExceptionListener, EventDispatcher and the Framework class itself. This is all stored in a separate file(s) and can be conditionally included based on your environment. He shows how to register a custom listener, add parameters to the DIC configuration.