Thank you for your response, it helped quite a lot
To the errors: I retested the named methods.
I guess it's some kind of false server configuration (using XAMPP as localhost). When uploading the test script to my online server, all this methods work fine. If I have the time, I will take a deeper look onto this problem, maybe I can find the cause of it
EDIT: ManiaConnect->getManialinks() is now working fine, too

So it's only the Ranking methods, which fail on my localhost.
EDIT2: Oh, the other methods seems to work on localhost, too. So uh... yeah, problem seems to be fixed now
