class method from another class

[eluser]Avril[/eluser]
euh ok, didn't know that it shouldn't be in a controller, I've checked a tutorial about this, and he did put it in a controller.

Question, is it a better security if I put it in a library rather then in a controller?
This small project is for local use, but I'm in a learning process and would like to have it as a real online application, this way it's a good exercise.

Thanks!