I use models for that. I don't think Helpers have anything in common with controllers.

I realize I gave pretty bad examples here - I'm more aiming at functionality that doesn't pertain to a single model, but rather just helper classes that are useful for a bunch of different controllers/models. Essentially just normal helper functions that are useful to a few controllers.

I also normally wouldn't want to stuff my models with a lot of app-level logic, like you mentioned, in MVCs I've used in the past - is that something that's normally done in Laravel?

looking for something like this myself.

In past worked on codeigniter where you can use different classes in controllers.