The proxy mechanism would only help by not forking the AOLserver process, but it still doesn't address the issue of each PHP script evaluation means getting a fresh PHP interpreter.
However, this just occurred to me: one could write a "PHP server" -- a long-running daemon-like process written in PHP that listened on a socket, where clients would connect to it and feed it a PHP script which PHP would pass through eval() and return the result.
*shudder* I think I'm going to have nightmares now. Maybe I'll implement something like this for shits and giggles, but frankly it's Just Not Right(tm).
-- Dossy