- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$time_begin = strtotime("2012-02-03");
$time_end = strtotime("2014-03-12");
$time_differ = $time_end - $time_begin;
$year_differ = date('Y', $time_differ);
$month_differ = date('m', $time_differ);
echo 12*intval($year_differ-1970)+intval($month_differ)-1;