"I don't think Ben or Don are devoting oodles of time to keeping the site alive (are you?). "
I'm not sure if that was meant to be a flame. Regardless, I can't defend PHP on any technical merit. It's got strengths and weaknesses.
Whether or not PHP sucks isn't this issue -- I do think the project has great documentation. (when the site works, that is!)
Each page thoroughly documents _what_ a function does, and _how_ to use it. The comments are the icing on the cake, because they more often than not tell you how to avoid the pitfalls of coding a site with PHP. I think that OpenACS could absolutely benefit from such a structure, because it promotes steady evolution of the man pages. (I can only imagine that when PHP started, the docs were horrendous, because of minimal community input.)
I have no idea how PHP docs are maintained (ie, is there a team? do individuals maintain certain procs and functions, etc..) Something to investigate...
