- var_dump: documentation ( source)
- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$time1 = strtotime('00:00:00');
$time2 = strtotime('00:00:07');
$diff = $time2 - $time1;
var_dump($time1,$time2,$diff);
$diff = date('H:i:s', $diff);
echo $diff;