My worries were largely related to the PHP engine having to effectively parse and interpret every included class on each page load. I discovered this was just my misunderstanding of the best way to configure a PHP server. After doing some research, I found that by using a combination of Apache 2's worker threads, FastCGI, and a PHP accelerator, this was no longer a problem. Any class or script loading overhead was only encountered on the first page load. Subsequent page loads were of comparative performance to a typical Java application. Making these configuration changes were trivial and generated massive performance gains.
Running PHP in CGI mode, together with FastCGI+optimizer is better than running mod_php? That is really surprising. I'll have to look at this more.
Tags: php, fastcgi