Simplest way to profile a PHP script

What's the easiest way to profile a PHP script? I'd love tacking something on that shows me a dump of all function calls and how long they took, but I'm also OK with putting something around specific functions. I tried experimenting with the [microtime][1] function: $then = microtime(); myFunc(); $now = microtime(); echo sprintf("Elapsed: %f", $now-$then); But that sometimes gives me negative results. Plus it's a lot of trouble to sprinkle that all over my code. [1]: http://php.net/microtime