First I must strongly advise that you never, ever design a Web
application that depends on the back button. This is a key
characteristic of a poorly designed application in most cases and is
worth a second look.
Glancing at the HTTP headers you are sending, two things stand out to
me. First, I am not sure that both Cache-Control headers will get sent.
Even if they are, I am not sure that you're going to see consistency
with Web browsers handling the multiple Cache-Control headers. Some HTTP
headers are intended to be used in multiple instances, such as
Set-Cookie, but Cache-Control is not one. Thus, you should specify your
directives in a single Cache-Control header.
In addition, many versions of Internet Explorer are known to ignore the
no-store directive. This directive does not allow even the storage of a
resource on your local computer. The message you see is being given by a
browser that actually adheres to this directive. Only non-compliant
browsers will not show this warning.
Either way, however, you eliminate just about any form of caching with a
compliant Web browser with all of the headers you are sending, and it
sounds like you specifically want the browser to cache a
previously-viewed page. So, you're going to have to make up your mind.
:-) The best first step for you to take is to learn what those headers
mean that you are sending.
>I am having trouble with sessions. I've created a user login/password
>section that uses session variables. Within this section, I have a form
>where the user enters data and submits. When the user clicks on the Browser
>back button, they should get back to the form with their data intact. This
>is indeed what happens most of the time but some users report that they get
>the following message after clicking on "Back":
>Warning: Page has Expired The page you requested was created using
>information you submitted in a form. This page is no longer available. As a
>security precaution, Internet Explorer does not automatically resubmit your
>information for you.
>To resubmit your information and view this Web page, click the Refresh
>When the refresh, their data is gone!!! I've gone through the docs and
>placed the following headers at the top of every file. Why is this
>happening and to only a few users???
>header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
>header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
>header("Cache-Control: no-store, no-cache, must-revalidate");
>header("Cache-Control: post-check=0, pre-check=0", false);
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