RE: JSP vs. PHP - Two vs. Three Teir

We started off using a classic three tier system - linux/Apache/PHP web server, linux/C++ daemon transaction server and Sun/Solaris/Oracle database. We found that when our site got busy (200+ users per webserver), the overhead of passing data to/from the transaction server was considerable. We went to two CPUs per webserver and placed all of the logic for the transaction server into PHP that ran on the webserver. We can now scale by adding new webservers, the first candidates being the old transaction servers. I think of this approach as a "logical" 3 tier approach. I really like doing everything in PHP, it's fast to develop on, it runs quickly and reliably (we're still using beta2 of version 4!) and in the end, our bottleneck is our database. I don't think the stuff they push in books has a whole lot to do w/real world web traffic. <sound of two pennies hitting table>