Getting a time difference in mongoDB?

I'm using PHP + mongoDB.

How c开发者_JS百科an I get a time difference between two time values?

I have a real time value which is string

$realtime = "2010-01-01 12:00:00";

and another value which is unixstamp time,

$mongotime = new Mongodate(strtotime($realtime));

So I can use either a string time value or unix time stamp.

But I'm not sure the way to get time difference between two values.

Should I just subtract two $mongotime values and does it give me a time difference in seconds?

If you have 2 unix timestamps...

$date  = $item['pubdate'];
(etc ...)
$unix_now = time();
$result = strtotime($date, $unix_now);
$unix_diff_min = (($unix_now  - $result) / 60);
$min = round($unix_diff_min);

This will give number of mins between the 2 timestamps...