$date = '2012.11.13';
$dateOfReturn = '2017.10.31';
$substract = str_replace('.', '-', $date);
$substract2 = str_replace('.', '-', $dateOfReturn);
$date1 = $substract;
$date2 = $substract2;
$ts1 = strtotime($date1);
$ts2 = strtotime($date2);
$year1 = date('Y', $ts1);
$year2 = date('Y', $ts2);
$month1 = date('m', $ts1);
$month2 = date('m', $ts2);
echo $diff = (($year2 - $year1) * 12) + ($month2 - $month1);