In CakePHP you declare what models you're going to use in a controller by defining $uses variable. You can also define it in AppController to have a certain set of models available in every controller. However be careful when doing it because you may put yourself in an unexpected situation as I did recently.

As soon as he made his script include a 'User' model in every quest, his logins stopped working. His script errored with a "Database table sessions for model Session was not found" message and refused to work. Digging deeper, he found that CakePHP merges an AppController's $uses value with the SessionControler's values. One overrides the other and your 'User' gets lost in the shuffle.

Do you have a rational explanation for such behavior? I have none. It's very unintuitive for me.