Avoiding form resubmit in php when pressing f5
Solution 1:
Your method could work in theory, but there's a much easier way.
After submitting the form successfully, perform a redirect. It doesn't matter where to, but it'll clear the $_POST.
header('Location: http://www.example.com/form.php');
In your case, it sounds like you want to redirect to the page you're already on. Append a $_GET parameter to the URL if you want to display a confirmation message.
Hope this helps,
Tom
Solution 2:
The solution is a pattern commonly known as Post/Redirect/Get