- time: documentation ( source)
- mktime: documentation ( source)
<?php $target_days = mktime(0,0,0,12,31,2013);// modify the birth day 12/31/2013
$today = time(); $diff_days = ($target_days - $today);
$days = (int)($diff_days/86400);
print "Days till next birthday: $days days!";
?>