Subtracting unix timestamp woes

[Beauford2]

I don't know why I hve such a hard time with this, what I'm trying to do isn't rocket science.

I have a subscription site where users are responsible for updating their own subscriptions. If they do it earlier than the end date. I want to calulate the difference so they don't loose what is remaining on the old one.

So for example. They subscribe for a month on July 5, 2009. Which means it expires on August 5, 2009.

If for some reason they renewed their subscription on July 8th for another month, the expiry should be September 5th, 2009. The best I can do is June 24, 1952.

Ain't that a hoot.

So I need a way to calculate the difference between July 5 and July 8 (or any other dates that will come up) so I get the right expirly date.

Any help is appreciated. This has to be in unix_timestamps as this is what I am using.

No code as nothing works.

Thanks

[dagon]

it really would help if you shwoed some code, even it does not work. Where\how are the dates stored?

[rthconsultants]

function dateDiff ($iStartDate, $iEndDate) {

return sprintf('%d', (strtotime($iEndDate) - strtotime($iStartDate)) / 86400);
}

$iDiff = dateDiff('2008-05-29', '2008-06-01');

echo "Distance between two dates is {$iDiff} days."; 

If though you have timestampes in a mysql database you can do some magic with DATEDIFF.