Properly bundling Symfony 2 web applications on the same host?

Question

symfony

Friends.
There are several projects on Symfony 2.1.0 (photo, video, audio) contests.
The task is to combine them on one host, so that the administrator has the ability to switch the active contest to the return of the frontend to clients, and the backend of all contests remains always active.
Tell me the best practices for merging sites on Symfony 2 with the ability to switch the active application. Accordingly, active routings, application configs should change. The system of authorization/authentication in the admin part is the same for all admin parts.