How do you handle the multiple form submit problem?
The problem I am seeing is with forms that take a bit of processing so they take around 10 seconds to process and complete all the needed actions before sending the user to the success/failure page. On these forms the user may get impatient and click the submit button again causing the data to be submitted twice.
The solution to the problem in my mind is fairly complex as it involves creating an md5 hash on the values in the form that should always be unique and saving that hash in the user's session so that if they try to submit the same form again during their session it will block the second submit. This allows the user to still use their browser's back button to get back to the form and they can modify the fields and submit the form again with the new values. As long as the new values are unique then their md5 hash will be different and the submit will work fine.
Does anyone see any problems with this approach or perhaps a better/simpler/easier way to accomplish the same thing?