“You’ll have issues” was my way of saying “I wouldn’t recommend them.” IMO if you want to run in a loop, pick a language where that’s the standard practice.

I find some of the language around FrankenPHP difficult to parse - is FrankenPHP always in loop mode (ala ReactPHP) or is it simply an option? I can't tell.. my gut reaction upon reading the intro material is that they "simply" replaced Apache/Nginx with Go's inbuilt, and much lighter, server structure and that PHP itself is left to run completely isolated as per usual?!

edit: indeed https://frankenphp.dev/docs/classic/ indicates normal runner capability similar to Apache.