How to measure the execution time of your Drupal scripts

While doing Drupal development, you sometimes might want to find out how fast or slow a certain part in your code is. Did you know that Drupal has 3 easy functions to do this built right in to core, timer_start($name), timer_read($name) and timer_stop($name).

You can have multiple timers in one run and each one of them is identified by the $name parameter you have to pass to each of these three functions.
I think the functions are pretty self explanatory:

• timer_start starts a timer
• timer_read tells you how long the timer has been running
• and timer_stop stops the timer and returns an array that contains the number of times the timer has been started and stopped (count) and the accumulated timer value in ms (time).

Source: http://www.drupalcoder.com/story/336-how-to-measure-the-execution-time-o...