Mike Willbanks has posted an introduction he's written up giving some helpful hints at tuning your servers and PHP applications for performance.

The focus of this post is not to show performance related items to specific PHP frameworks since many bottlenecks actually apply before running the framework itself that should certainly be solved up front. Therefore in this posting I attempt to look at simple items that can be deployed in order to produce finer tuned systems.

He talks about a few different aspects:

• PHP Performance Tuning (opcode caching, apc file priming, includes, loops, etc)
• RDBMS Performance Tuning (indexes in queries, query caching, archiving)
• HTTP Performance Tuning (content compression, css sprites, limit modules, etc)

Leon Chevalier has posted about a class he's developed (you can download it here) that can help to speed up the load times for your site.

There are 4 relatively easy ways by which you can speed up the time it takes a browser to download a page. Following on from my post on joining CSS and JavaScript files, I have written a PHP script which will automatically do all of the above.

He gives example code of the class in action and includes some screenshots of the benchmarks from the YSlow Firefox extension showing the improvements.