Back button re-submit form data ($_POST)

My problem is that the back button causes the browser to say something like "Page expired" when the previous page was created by a form.

Example:

• page1: form submitted with search criterias ($_POST request, form points to page2)
• page2: Receives $_POST request and show result (list of user with links, points to page3)
• page3: Show user profile

Now when the visitor clicks the back button in the browser it开发者_运维技巧 will show something like "Page expired".

Instead the previous page should be shown with no warnings (page2, with the userlist)

How are your strategies to get around this behavior?

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If you are submitting a form with search parameters, you are trying to get some data, not modify some.

So, you should use the HTTP GET method, and not POST : POST should be used when you intend to create/modify data, and GET should be used when you intend to fetch some data.

Or, if you have some create/modify operation that has to be done :

• The form first POSTs to a first page
  • That page does some operations (like writing something to a database)
  • And then redirects to another page, using a Location HTTP header.
• It's that last page, that's queries by the browser using a GET requests, that displays the data fetched from the parameters received in the URL.

See the Post/Redirect/Get page on wikipedia, about this.

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Use the Post/Redirect/Get (PRG) Pattern.

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This applies to PHP and IE8.

Not only must you set cacheing to private, but you must remove the 4 cacheing headers and this can only be done with PHP 5.3. In PHP 5.2 you can only set the 4 headers to blank values if using the Zend Framework's setHeader() method. For some reason is not sufficient on IE8 to set the 4 header values to empty values. Here's the code for PHP 5.3:

    header_remove("Expires");
    header_remove("Cache-Control");
    header_remove("Pragma");
    header_remove("Last-Modified");

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Send a Location header in the script you POSTed to, pointing to the page that comes after.

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Don't use POST for search. Search can safely be done with GET since it won't alter anything.

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You can use session to do this.

eg.

$_SESSION['name'] = $_POST['name'];

Remember to unset your variables after the process is complete to optimize memory usage.