Maybe you are not familiar with PHP multithreading in recent times but I have been using https://github.com/krakjoe/pthreads and works perfectly. No process forking.
Haven't been following php in years, but from back in the day I remember many different approaches trying to introduce threads and none could guarantee safety for the fundamental reason that the language itself is implemented unsafely. The runtime was done in C with unsafe features from the start. So process forking was the only sane reason to run php. I don't know how much of that is still true, though.
No native support for concurrency operators, no real event loop implementation, lack built-in support for non-blocking IO...
I do Elixir regularly and Actor Model is not something PHP developers know
Is this just a long way of saying it doesn’t have “async” because threads are a perfectly fine concurrency primitive that you can build event loops on top of.
Maybe you are not familiar with PHP multithreading in recent times but I have been using https://github.com/krakjoe/pthreads and works perfectly. No process forking.