How to display messages to the user after a POST + HTTP redirect

Question

I’m using the PRG pattern to avoid multiple form submission. It has, however, a serious drawback — you cannot simply echo the confirmation message to the user (

Answer 1

Coming very late to this discussion..

You could use a combination of the two proposed options.

After the POST request the client is redirected (303) to an URL indicating that there could be a response message for this request:

Client: GET  http://example.com/foo.cgi
Server: 200  Ok

Client: POST http://example.com/bar.cgi
Server: 303  http://example.com/foo.cgi?msg=true

If the msg argument is true the message will be looked up in the session and (if found) included in the response to the client.
If the msg argument is ! true (or not present), the lookup step is skipped.

With this solution, you prevent the actual message being show in the URL, the URL only indicates there could be a message. Also, the message is only shown when needed (=when found in the session).

Another advantage is that this solution also allows for proper cash-controls to be included with HTTP responses.