How could set a date and get a countdown in PHP? For example if I set the date as 3 December 2PM it would tell me how many days and hours are remaining.
No need for
You can use the strtotime function to get the time of the date specified, then use time to get the difference.
$date = strtotime("December 3, 2009 2:00 PM");
$remaining = $date - time();
$remaining will be the number of seconds remaining. Then you can divide that number to get the number of days, hours, minutes, etc.
$days_remaining = floor($remaining / 86400);
$hours_remaining = floor(($remaining % 86400) / 3600);
echo "There are $days_remaining days and $hours_remaining hours left";