Yes. The PHP process keeps running but resets completely on every request. The bytecode is cached though, so loading the code shouldn't add much overhead.

PHP can be used for long-running jobs, but it doesn't have very good garbage collection, and has no language-level concurrency and very little asynchronicity.

Well, you could daemonize a PHP process, which would listen to some port, and parse the requests. It's like implementing your web server in PHP.

The problem with it is, one request can bring the whole thing down.