get future or past date php

// now
$now = date('y-m-d');

// 1 month forward
$month = date('y-m-d', strtotime('+1 months'));

//25 days back
$day = date('y-m-d', strtotime('-25 days'));

//1 year forward
$year = date('y-m-d', strtotime('+1 years'));