I see the point to make a parallel with HipHop, but here YJIT is directly integrated in CRuby, the main implementation of the language, and it’s just a matter of command line flag whether you enable or disable it — at least from what I remember that I red.

From what I remember, HipHop was distributed in a different toolchain than the vanilla PHP interpreter. Ruby also have other interpreters available by the way: https://github.com/codicoscepticos/ruby-implementations