Difference between 2 dates in seconds [duplicate]

This question already has answers here: Get interval seconds between two datetime in PHP? (8 answers) Closed last month.

In my project, I need to calculate the difference in seconds between two dates:

For example:

$firstDay = "2011-05-12 18:20:20";
$secondDay = "2011-05-13 18:20:20";

Then I should get 86400 Seconds That is 24 hours.

Similarly for

$firstDay = "2011-05-13 11:59:20";
$secondDay = "2011-05-13 12:00:20";

It should return 60 Seconds.

I read lots 开发者_如何学Goof questions on Stack Overflow but they only deal with the difference between 2 minute fields like 11:50:01 and 12:10:57

---

$timeFirst  = strtotime('2011-05-12 18:20:20');
$timeSecond = strtotime('2011-05-13 18:20:20');
$differenceInSeconds = $timeSecond - $timeFirst;

You will then be able to use the seconds to find minutes, hours, days, etc.