I don't think it's the same. mod_perl really is the same perl process just running different functions for each page. The typical configuration for PHP offers more isolation than mod_perl does under any configuration I'm aware of. We'd have to prevent one mod_perl page from being able to see other mod_perl pages by proxy of the symbol table or other interpreter globals. To do that, we really do need separate processes. I think we solve this by using FastCGI, the same thing that I hear Rails typically runs on.