You definitely need a new oAuth Token everytime you log in. It doesn’t matter if you login als Bot or as normal User. The stream key keeps the same. Our problem is, you can’t generate a oAuth Token by server-script - well, we still don’t have an idea how to do it.
TL;DR
There is no possibility for the PHP-Script to log in into api.twitch.tv to get a code, which is nessecary for us to generate the oAuth. Or did I miss something?