Subscribtion system in PHP

I would like to build a user validity system with a subscribtion system working with date.
In MySQL I have a filed(date format) with the date in this format: YYYY-DD-MM.
That date + an expiration time ($expire = 365*$abo*3600; where $abo is the month (1-12))

I need to compare that result with the today date

$expire = 365*$abo*3600;
$subscribe = $subscribedate+$expire;
$date = date("Ymd")*1;


if ($subscribe > $date1) {
echo"Abo OK<br>";
} else {
echo"Not OK<br>";
}

What could I do that the small script works????
Thanks for your help