There are times when you need to debug on what time does a process required. This small snippet perhaps can show you how:

 $time = microtime();
 $time = explode(' ', $time);
 $time = $time[1] + $time[0];
 $start = $time;


//SOME PROCESS GOES HERE


  $time = microtime();
  $time = explode(' ', $time);
  $time = $time[1] + $time[0];
  $finish = $time;
  $total_time = round(($finish - $start), 4);

echo 'Process finished in '.$total_time.' seconds.';
die();

This snippet helps me a ton when i have to debug a complaint from one of my client... and hope it can helps you too!