It's a cool idea but I haven't explored this in detail so I don't have a good answer. I haven't touched PHP in 2 years but they have a new feature which might achieve some of those design goals you mentioned:

https://www.php.net/manual/en/opcache.preloading.php

> preload.php is an arbitrary file that will run once at server startup (PHP-FPM, mod_php, etc.) and load code into persistent memory.

It's interesting to me, because in a big ecomm framework we were getting 80ms PHP page loads, with something like preload it could probably be moved down to 25 or 30ms.

This is one of the things FrankenPHP is dealing with (w/out fork).

The big 'gotcha' here is that the heap is typically shared amongst threads in a process and that's where globals tend to live. However, you could make a heap per thread (which is kind of how some implementations of isolates work). You lose a bit of perf by doing this but it does deal with the global stomping problem.

We've (NanoVMs) looked at this a few times. It can be done but as bdg mentioned most frameworks expect state to be in a completely clear so the real challenge is that you have to go in and deal with each framework itself (for instance using WP as an example).

Anyways, I thought FrankenPHP was pretty cool so went ahead and package it up for Nanos: https://repo.ops.city/v2/packages/eyberg/frankenphp/0.0.1/x8... .

If you had a php framework that wasn't so dependent on global state you could definitely make something way more performant.

In general scripting languages and their usage of global state is a recurring concurrency issue but I'm hopeful that the isolate pattern will catch on in other languages to help alleviate it.