I am a software engineer and an expert in MVC Yii Framework. I have an experience of 4+ in development of big applications using Yii framework which is a very stable framework. Actually i have make two big applications:
-An Eticketing application for a big travel agency of trains. Through this application, people can bye tickets by web, mobile payment terminal, seft service kiosk and smartphone. The services of the applications are exposed through the web service technology
-An application for whole university management (management of students, management of fees, management of registration, management of information sharing; etc...). This application can also take into account the management of many universities in the same platform.
For those, i think i can migrate your website from your architecture to MVC architecture using the stable Yii framework because i have a strong experience in this framework.