PHP only works like that because Apache's default process model is process-per-request. Anything event based requires moving PHP in to multiple fcgi worker proc

PHP only works like that because Apache's default process model is process-per-request. Anything event based requires moving PHP in to multiple fcgi worker processes, and then you get limited by that. A fast, non-shared interpreter could work very well in a threaded server, or a threaded backend to an event-based server.