User is asked only once, the guest is asked every time.
Checking with google chrome, i made various posts as guest and php 8.0.1, it works. I will test more, but if i don't say anything more about it, it means that it works fine, thank you Visman, you're the best
EDIT : i made other posts with Google Chrome and Firefox, everything is fine in both, the question is not still the same so the random function works fine (there are 2 questions possible) and it worked each post. I tried with php 7.4, it works fine too.
P.S. I don't use Chrome (it transfers too much data to Google).
And i guess you're right, as i use Linux Mint, i may better use Chromium or Firefox.