Use This one and you can get the
$previousDate = '2013-7-26 17:01:10';
$startdate = new DateTime($previousDate);
$endDate = new DateTime('now');
$interval = $endDate->diff($startdate);
echo$interval->format('%y years, %m months, %d days');
Refer this
http://ca2.php.net/manual/en/dateinterval.format.php