My article on performance has just been published in Oracle Technology Network, you can read it at:
http://www.oracle.com/technology/pub/articles/deployphp/alshanetsky_deployphp.html
The article has some Oracle and Oracle httpd (variant of Apache) specific optimization, however for the most part it can be applied to virtually any PHP installation. To those interested in improving the speed of their PHP application it should (I hope) prove to be an interesting read.