My two cents:

9 times out of 10 I'll keep frontend and backend in separate apps. I like my code clean and simple, and looking at an action file with a million methods gives me a headache… same with the routing file— that can get pretty ugly if you're explicitly naming all of your routes.

Another good reason is portability. If you decide later you want your administrative functionality to live under a different domain name, it's a cinch if that functionality has its own app.

Finally, I much prefer to assign credential requirements on a module-by-module basis, rather than on an action-by-action basis. That gets messy, and it's easy to forget to secure an action here or there, especially if you've got a ton of them, and rename them, etc…

Also, I find that I very rarely duplicate any code between the two apps. If you've got wicked long controller actions, that might be a sign that you should leverage more functionality to your model.

documented on: 25 June 2007, east3rd

I'd like to separate backend and frontend, too… but with the plugins I'd very like to use (sfGuardPlugin, sfSimpleCMSPlugin, sfSimpleBlogPlugin), I didn't find out how to separate the *Admin-Modules of the Plugins in an own app.

Doesn't work this or do I have to add very much routes? Or is there an "easy" way?

documented on: 22 August 2007, mix

I wish both backend and frontend would be together.

For example, in my cms I want the backend to be able to access the routing and the custom helpers that were build for frontend.

documented on: 22 August 2007, z01d