Measure the time spent in a piece of code. Extracted from Drupal database layer.

PHP measure code time

<?php

list($usec, $sec) = explode(' ', microtime());
$timer = (float)$usec + (float)$sec;

//
// YOUR CODE HERE
//

list($usec, $sec) = explode(' ', microtime());
$stop = (float)$usec + (float)$sec;
$diff = $stop - $timer;

// Diff contains a float in seconds