I started TouristEye.com 4 years ago with Symfony 1.1. We kept pace with the new releases (updating when 1.2.2, 1.3.2, 1.4.2 was out). Last November we decided

I started TouristEye.com 4 years ago with Symfony 1.1. We kept pace with the new releases (updating when 1.2.2, 1.3.2, 1.4.2 was out). Last November we decided to simplify our website and completely change our website, so we felt it was the right time to do the migration. It took 5 months (myself as the backend of the website & api, and another developer as the frontend). It was a big rewrite, but the code now is so much better to maintain and learn. We are right now using 2.3, and I'm way happy coding :) About your case, I agree with you that the best way for you is to add component by component, extracting and encapsulating functionality so you can use Symfony2, Zend or whatever framework you want in the future. Go for a service oriented architecture. And let's hope you have everything tested!