Sometimes there is issue we got double records in the database due to the form submitted twice.

Here is the way how to prevent it. A simple way

session_start();    
if (!$_SESSION['post_data'] == $_POST)
{
// process the data
// after success process, set the session to post value
    $_SESSION['post_data'] = $_POST;
}
else
{
// display a message that the form already submitted. 
}