How to calculate difference between two dates in hour using PHP?

This is pretty easy thing but sometimes we forget actually how we can calculate this. PHP Manual is a root source for this solution but sometimes its also time consuming to search and find the procedure.

Here I am just writing to memorize if you forgot already 🙂

$ts1 = strtotime('03-09-2013 04:48');
$ts2 = strtotime('02-09-2013 12:12');
$diff = abs($ts1 - $ts2) / 3600;     

If you want to find difference in day/minute/seconds then you need to change something in above code. Its your challenge to find the way..