In my experience, PHP can have really unexpected runtime performance. This site has some interesting benchmarks highlighting this: http://www.phpbench.com/ http

In my experience, PHP can have really unexpected runtime performance. This site has some interesting benchmarks highlighting this: http://www.phpbench.com/ http://www.phpbench.com/ I'd like to hear of any other PHP performance gotchas people know of. One of my favorites: passing function arguments by value is faster than passing by reference.