Of course, there's a vast ecosystem still running shopping carts, forums and whatnot. It's much more prevalent that you seem to think. Just because it's not cool anymore (or well ever) doesn't mean it's dead.
That's a very dated view of PHP. Modern PHP is far "cooler" than it was a few years ago. Just look at the entire https://laravel.com ecosystem — the most starred web framework on all of GitHub, across all languages, is Laravel.
Discovering Laravel a couple of years ago was perhaps one of the most significant things that made PHP interesting again after 20+ years of working with PHP.
It's refreshing (as far as PHP goes) and worth checking out with an open mind. Performance on the other hand, that take a little more work.
Performance keeps getting better, particularly with PHP 7 and 8. And just last week, “Laravel Octane” was announced... it lets you serve a Laravel app using Swoole, and early benchmarks on a MacBook Pro suggest 25k+ HTTP requests served per second!
Laravel Octane is using Swoole which implements a complete webserver, so there won‘t be any php-fpm more. As you would need to restart the server for every code change, there won‘t be a performance difference between docker on mac and non-docker.
Oh, I get that, it was more directed at the OP. It's not your Rust, Nim or Crystal or... which is what I meant about 'cool'. Coolness is always in the eye of the beholder :)
Facebook wrote a new runtime and has, over time, changed the language rather significantly (eg strong static typing, async/await, generics, overhauled much of the standard library.) It's called Hack. At this point, I don't think you could reasonably say facebook's written in php any more than you could say various c++ projects are written in C.