php count second different

1<?php
2
3$hour1 = '12:00:00';
4$hour2 = '09:00:00';
5
6$o1 = new DateTime($hour1);
7$o2 = new DateTime($hour2);
8
9$diff = $o1->diff($o2,true); // to make the difference to be always positive.
10
11echo $diff->format('%H:%I:%S');
12