This sounds very plausible to me. As well as PHP, I've written a bunch of Java and threaded Java. I treat the latter two as different languages: yes you can use

This sounds very plausible to me. As well as PHP, I've written a bunch of Java and threaded Java. I treat the latter two as different languages: yes you can use the same parser for both, but adding threads to the semantics also removes a lot of the mental models and assumptions we could previously make.