Yes, though heavy optimization in opcode caching and JIT keeps it fast and the primary process manager today (php-fpm) generally keeps a pool of PHP processes persistent. Each request is initialized from scratch but there's no disk nor interpreter hit after the first.
There are, of course, frameworks that simply handle HTTP requests directly (amphp, swoole) that operate as persistent application servers, so state is maintained.
> Does this model uses OS threads? Does it uses green threads?
No. PHP webserver backends are generally a long-lived forking model.
> I feel like the Go model is a way better model for server software than async
Swoole [1] offers a coroutine and channel model. It's incredibly fast and the techempower benchmarks [2] attest to the raw speed.
> It feels a bit weird to see how full of objects PHP is
Agreed. It's often way over the top with Java-esque OOP complexity. It does depend on the libraries in question but the popular ones are very heavy (Symfony). You can of course write very simple imperative code just fine too.
