The main thing i want to solve is to check user session when somebody want to access admin panel. I\'ve created MY_Controller class and placed it in library.
I got this error on a project as I'm learning CodeIgniter. My solution was to, to use your project as an example, require_once('MY_Controller'); at the top my new Controller.
That way I didn't have to move my file to the core and I could keep it in my directory of Controllers.