First problem is that I screwed up copying the code from GitHub, that's corrected now. I'll check for the JSON library, thanks!
At least I'm getting the actual temp now, great

Wow you are quick, thanks! It makes clear that the Tado change and my "mess" was a coincidence: I still get these results from running the php file:
Token Age: 2 | Used cached token | PHP Notice: Undefined index: homes in /home/pi/domoticz/scripts/tado.php on line 134
PHP Notice: Undefined index ...

Tado changed the API and unfortunately since it is not published, was not known. They've introduced 'client_secret' requirement, so the code has been modified (I think the client_secret is the same for all users and linked to the app/client). The code on GitHub has been updated and is working again ...