- date: documentation ( source)
- strtotime: documentation ( source)
<?php
echo date('2013-02-28', strtotime(date('Y-m-d').' + 1 month'));
echo ' ';
echo date('Y-m-d', strtotime(date('Y-m-d').' + 2 month'));
echo ' ';
echo date('Y-m-d', strtotime(date('Y-m-d').' + 3 month'));