That's distinct from JIT - it's just a way to prevent having to re-parse/compile to byte code every single request to your site (no other language has this issue)
Because no other language is as easy to deploy. With PHP you edit the PHP file, and that's it. It's deployed. No clearing cache, no compiling, packaging, nothing.
It's one of the major factors in how good of a language it is.
If it's needs this optimization as a result of that, it's completely worth it, and other languages should copy that.
Nah, it's because PHP isn't an actively running process.
The overhead of starting a process isn't what it used to be in shared web infra world before. It's cheap to spin up a small VM now. And there are other similar constructs, e.g. FaaS
