private function diffMicrotime($start, $end)
{
list($start_usec, $start_sec) = explode(" ", $start);
list($end_usec, $end_sec) = explode(" ", $end);
$diff_sec = (int) $end_sec - (int) $start_sec;
$diff_usec = (double) $end_usec - (double) $start_usec;
return (double) $diff_sec + $diff_usec;
}