Question

I have the following code to calculate the execution time.

$TimeTaken['start'] = microtime();
require_once 'resources/include.php'; 
session_start();

ob_start();
error_reporting(E_ALL);*/
error_reporting(0);

/* Other Mojo
  ...............
  ...............
  ...............
*/

ob_flush();
flush();
ob_end_flush();

$TimeTaken['end']   = microtime();
$TimeTaken['diff'] = $TimeTaken['end'] - $TimeTaken['start'];
print_r($TimeTaken);
?>

This is the output that i got (sometimes)

Array ( [start] => 0.72150600 1329728036 
        [end] => 0.62957200 1329728038 
        [diff] => -0.091934 )

Is the above code right and if so why is start time > end time

Answer 1

Because the valid way to get the time with microseconds is microtime(true);, not microtime();

Without second parameter equal to true you just have a string 0.72150600 1329728036 that represents the second fractions and seconds since unix epoch separated by space. And subtraction operator just casts it to the 0.72150600 which is just wrong.