php date back 1 month code example
Example 1: +1 month php
$time = strtotime("2010.12.11");
$final = date("Y-m-d", strtotime("+1 month", $time));
Example 2: php date today plus 1 month
$future_timestamp = strtotime("+1 month");
$data = date('Y-m-d', $future_timestamp);