- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$todayDate = date("2011-01-31");
//Add one day to today
$dateOneMonthAdded = strtotime(date("Y-m-d", strtotime($todayDate)) . "+1 month");
echo "After adding one month: ".date('Y-m-d', $dateOneMonthAdded)."<br>";