在现有日期添加月份？

Question

I have a date where I need to add months to, but somehow it returns the epoch date

$duration = 28;
$row['end_date'] = '2010-09-22 0000:00:00';

$newEndDate =  date("Y-m-d", strtotime(" +".$duration." month",substr($row['end_date'],0,10)));

Answer 1

$newEndDate = strtotime(date("Y-m-d", strtotime($date)) . " +1 month");