CI2 to CI3: Call to a member function helper() on a non-object in ...Session.php

Thx, that solved the previous error but now I've a new one:

Code:

Unable to locate the specified class: Session.php

If I comment the new Plan_Events() line the error is gone, so the problem seems to be related to the own class extending CI_Controller.

As I quoted at the first post the Plan_Events class only extends the CI_Controller class and have some public functions using CI models. It doesn't use sessions.

Hints please...