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)