Well that sucks ... I guess the name Auto-Update made me trust in it a bit to much, lesson learned.
Of course it was on the only server i didn't set up and they forgot to include the froxlor db in the weekly db backup.
I think i try to install php 7 then beside php 5.6. If i remember correct it was php-fpm on an other debian jessie server that let me choose which site runs with which php version.
I could run froxlor with PHP 7 then and change the other sites one by one to php 7. Really bad timing, i had plans for summer 2020 to do that.