At Cogneato we’ve had a CMS that has been built up over more than a decade. We started working on a completely new system a while back to have a new and more powerful interface, add new features, and get rid of a lot of the cruft that the old system had from being developed over such a long period by many developers with different styles. We decided to use Doctrine as an ORM and Symfony as a framework for our back end.
We have maybe 200 sites running on various versions of our old system though, and we need to be able to add the new system’s features without having to completely redo them. We needed a way to be able to leave all the current stuff in place and pull in the Symfony stuff to the existing files with a simple include.