cool! With some minor tweaking, your code works! Thanks!
For those of you who needed this too...
$month = "$sel_month";
$mdate = getdate(mktime(0,0,0,$month,1,$year));
$total_days = strftime( "%d",mktime(0,0,0,$month+1,0,$year));
print "<select>";
for ($i=1; $i <= $total_days; $i++) {
print "<option>$i</option>";
}
print "</select>";
where $sel_month is selected from a previous page.