A few thing you could do:
- Make sure that the "action" attribute on your form leads to the correct destination.
- Try using $_REQUEST[] instead of $_POST, see if there is any change.
[Optional] Try including both a 'name' and an 'id' attribute e.g.
If you are in a Linux environment, check that you have both Read/Write permissions to the file.
In addition, this link might also help.
EDIT:
You could also substitute
if(isset($_POST['submit'])){
with this:
if($_SERVER['REQUEST_METHOD'] == "POST"){
This is always the best way of checking whether or not a form has been submitted
