backend in MVC pattern ??

[PHPycho]

Hello forums!!
I had some queries related to MVC pattern.
I used to perform the uri action as:
http://mysite.com/controller/method/params by default, I have used router tweaking for other than default routing.
I would like to hear your views about backend development in MVC pattern.
I had found in cakePHP, action_admin pattern in the same controller file(for both frontend and backend) .
and i dont know what goes in the rest framework.

I would like to know which method is more suitable and flexible for backend development
1> using same controller file for both backend and frontend apps
2> using different mvc folders for backend
3> using different controller for backend and frontend but with same model part
4> else
Please jott down your valueable views/suggestions.
Thanks in advance for the help.

[NogDog]

If the controller is adequately designed to implement sufficient user authentication logic in order to differentiate between regular users and those who should have access to the "back end" operations, I do not see any particular reason to have separate controllers/models.