[pilif]

> Then you could have person manually review pull his changes into manager (like Linus does with Linux)

this assumes that there are enough trusted people in the PHP project with enough time to spend for doing nothing but reviewing pull requests.

> The other option is submodules.

that's a very good idea, especially when you consider how modularized PHP's build system already is. Give them time though. Moving from SVN to git is already a huge step in the right direction, even though the keep most of the old model the same.

Once all of that works nicely, a further step can be to move to submodules.