I am having trouble with subtracting times in PHP.
My times are:
$row['exp'] = 2017-03-31
and date('Y-m-d') = 2017-03-10 (today)
$datetime1 = strtotime($row['exp']);
$datetime2 = strtotime(date('Y-m-d'));
$secs = $datetime1 - $datetime2;// == <seconds between the two times>
$days = $secs / 86400;
echo $days;
My result is:
36520.958333333333
Use the PHP DateTime class instead, it has built in functions, such as DateTime::diff, which seems to be what you're looking for. The DateTime objects are much easier to work with too.
$today = new DateTime('today');
$date = new DateTime("2017-03-31");
echo $today->diff($date)->d; // 21
Just pass your $row['exp'] as the parameter of $date instead, so you get
$date = new DateTime($row['exp']);
Although, I can't reproduce your issue with the given input you have, this live demo outputs "20.958333333333" (which is about right, you just need to ceil() it).