I understand that PHP supports handling multiple concurrent connections and depending on server it can be configured as mentioned in this [answer](https://stackoverflow.com/a/1430890/2159867)

How does server manages multiple connections does it forks a child process for each request or does it handle using threads or does it handles using a thread pool?

The [linked answer](https://stackoverflow.com/a/1430890/2159867) says a process is forked and then the author in comment says threads or process, which makes it confusing, if requests are served using child-processes, threads or thread pool?