Brandon Savage has a new post to his blog today with a few tips on some "micro" optimizations you can make to your PHP applications to improve performance and make for better maintainability.
Micro optimization doesn't work. So why, then, is this post called "micro optimizations that matter"? The optimizations below could be described as micro - not in the little amounts of performance improved, but in the very minute (if any) changes required to your code to make use of them. All of these optimizations are standard optimizations you should consider, and all of them will offer considerable performance enhancements.
Instead of the usual tips that might save you a millionth of a second here and there, Brandon suggests some smaller things like caching data, removing manual error logging, using a CDN and adding in an autoloader.