php - Prevent Back button from showing POST confirmation alert

Question

I have an application that supplies long list of parameters to a web page, so I have to use POST instead of GET. The problem is that when page gets displayed and user clicks the Back button, Firefox shows up a warning:

To display this page, Firefox must send information that will repeat any action (such as a search or order confirmation) that was performed earlier.

Since application is built in such way that going Back is a quite common operation, this is really annoying to end users.

Basically, I would like to do it the way this page does:

http://www.pikanya.net/testcache/

Enter something, submit, and click Back button. No warning, it just goes back.

Googling I found out that this might be a bug in Firefox 3, but I'd like to somehow get this behavior even after they "fix" it.

I guess it could be doable with some HTTP headers, but which exactly?

question from:https://stackoverflow.com/questions/660329/prevent-back-button-from-showing-post-confirmation-alert

Answer 1

One way round it is to redirect the POST to a page which redirects to a GET - see Post/Redirect/Get on wikipedia.

Say your POST is 4K of form data. Presumably your server does something with that data rather than just displaying it once and throwing it away, such as saving it in a database. Keep doing that, or if it's a huge search form create a temporary copy of it in a database that gets purged after a few days or on a LRU basis when a space limit is used. Now create a representation of the data which can be accessed using GET. If it's temporary, generate an ID for it and use that as the URL; if it's a permanent set of data it probably has an ID or something that can be used for the URL. At the worst case, an algorithm like tiny url uses can collapse a big URL to a much smaller one. Redirect the POST to GET the representation of the data.

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As a historical note, this technique was established practice in 1995.