What are some good PHP performance tips?

Question

I\'ve heard of some performance tips for PHP such as using strtr() over str_replace() over preg_replace() depending on the situation.

Answer 1

Usually pre-mature optimization is a veeeery bad idea. It really doesn't matter when you make your code run 0.5ms faster when single SQL query takes 80ms.

You should profile code and focus on bottle necks and then try things like caching (static, APC, Memcached). Microoptimizations are the very last step when you've got perfect application design and still need more performance from certain modules/functions.