Ok... I finally got it working as I wanted it to work.
But there is one thing I cannot solve yet:
Every time the script.php should be activated by Airio I am getting an entry in the Airio log that the script timed out...
I am not sure if the script is executed correctly though, because I changed it a bit to filter just some cars - not all cars available in the stats files. So I would have to wait until someone drives a new PB...
Any clue why I am getting a time out error? If I activate the script manually it works perfectly...