Yeah that's true, I misunderstood. He did mention in the talk that mod_perl was infeasible for this use case because it gave the user too much control. One us

Yeah that's true, I misunderstood. He did mention in the talk that mod_perl was infeasible for this use case because it gave the user too much control. One user could override the Apache base_dir and redirect another user's traffic to his pages!!! He said that as a result, hosting providers in the 90's would charge 100x the price for mod_perl hosting on a dedicated bare metal box, vs mod_php which could be shared. Didn't know that. So I guess the answer is that mod_php has to be careful and not expose too many Apache hooks to the user. The PHP interpreter does seem to have some unique qualities that make it good for embedding, compared with Perl, Python, Ruby.