Please let me give more details
$datetime1 = new DateTime($orderdate);
$datetime2 = new DateTime($currdate);
$interval = date_diff($datetime1, $datetime2);
$interval->format('%m months');
$months_diff = $interval->format('%m months');
for($i = 1; $i <=($months_diff+1); $i++){
$totalFees = $fees + $totalFees;