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 t

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?