Ibuildings techPortal: DPC Radio: Profiling PHP Applications
Note: This article was originally published at PHPDeveloper on 15 December 2011.
The web is full of useful advice focussed on pushing out the last bit of performance of your code. They mention trivial changes. like changing every occurrence of print with echo even suggesting to use for instead of foreach. These optimisations help, but you are not going to notice it unless they're in a tight loop with many iterations. It is also a wrong approach for tackling performance issues.