- floor: documentation ( source)
- strtotime: documentation ( source)
<?php
$confirm_date = strtotime('2015-09-19');
$today_date = strtotime('2015-09-17');
$diff = $confirm_date - $today_date;
$daysleft = floor($diff/86400);
if($daysleft == 2) { echo 'yes'; echo $daysleft; }