select the month form element, copy that code that gets generated, then select the year form element, and paste the mont in front of it, th
assuming the form elements are named exp_month and exp_year, the final code would look like this for the biding:
<?php echo((isset($_POST["exp_month"]))?$_POST["exp_month"]:"") ?><?php echo((isset($_POST["exp_year"]))?$_POST["exp_year"]:"") ?>