I've didn't think "no more PHP". I am just seeing how much non-PHP Meta open sources and talk with Meta guys at events who are building stuff for JS, talking about new client and varied tech stack and then you've told me "actually its still mostly PHP".

That’ll be because Facebook doesn’t use PHP as such, but Hack, which isn’t compatible with vanilla PHP. Hack isn’t really used much outside of Meta, so what’s the point of going through the extra work of open sourcing our stuff if nobody else will ever use it?