substract 2 dates php code example

Example 1: calculate time difference php

$time1 = new DateTime('09:00:59');
$time2 = new DateTime('09:01:00');
$interval = $time1->diff($time2);
echo $interval->format('%s second(s)');

Result: 1 second(s)

Example 2: substract 2 dates php

$datetime1 = strtotime('May 3, 2012 10:38:22 GMT');
$datetime2 = strtotime('06 Apr 2012 07:22:21 GMT');

$secs = $datetime2 - $datetime1;// == <seconds between the two times>
$days = $secs / 86400;