HOW TO ADD TWO DATES IN PHP
## CURRENT DATE + ANY DATES YOU WANT TO ADD
echo date("Y-m-d", strtotime($date."+5 days"));
echo date("Y-m-d", strtotime($date."+5 weeks"));
echo date("Y-m-d", strtotime($date."+5 months"));
echo date("Y-m-d", strtotime($date."+5 years"));
combine date and time in php
$combinedDT = date('Y-m-d H:i:s', strtotime("$date $time"));
^ ^
Source:stackoverflow.com
combine date time php