Post/Redirect/Get solution just for refreshing the page?

Question

PHP Post/Redirect/Get solution is good just for refreshing the page?

What about if the user clicks on the back button twice and resend the form? The only solution I have found is to check in my database if same data is already posted.

Is there any other solution without querying the database?

Thank you in advance!!!

Answer 1

PRG is perfect for browser Back button support too. An HTTP redirect replaces the URL in browser history instead of adding a new entry. If you apply PRG consistently, i.e. you always return a redirect from a POST, then browser history will only contain "safe" pages (GET), there will never be a POST URL in the history.

There is still a chance of getting duplicate form submissions, though. For example if the user double-clicks the submit button. So if you want to be extra safe you need some extra mechanism (e.g. nonce) to prevent double submissions.

Answer 2

PRG is used because of the nature of HTTP. POST is not a safe operation hence PRG is preferred.