[EDIT]
sorry... didn't see the double posting 😉
[/EDIT]
if you check the submission with something like
if($submit) { // some code}
// or
if($_POST['submit']) { // some code}
replace with
if($_POST['submit_x']) { // some code}
otherwise this could help and show you what values are incoming:
echo "<pre>";
print_r($_POST);
echo "</pre>";