If a piece of code needs to be executed in multiple controller actions it should be factored out and moved into a new class. Depending on the actual logic this new class can be an action filter/controller behavior, an application component or a simple static helper. This way you can avoid unnecessary coupling between controllers and don’t have to (ab)use the framework’s routing mechanism for a simple method call.
i think sometimes, is necessary, call actions from one controller to another, and it is the latter that is responsible for the response.
if after an action in the controller ‘a’ where I get a model car in the $ _GET and after certain operations want to show the view of the car it would make sense to call from the controller ‘a’ to CarController->actionView() to show the car