&quot;Warning: Page Expired&quot;

"Warning: Page Expired"

Anon

Hello!

I am writing about a quirk in Internet Explorer that I'm trying to work around.  Any idea's would be appreciated!

Background: Each page ends in the .php extension, and is an actual script.

The problem: page_a.php is a page+form, that submits information to page_b.php. page_b.php displays information that links to other php pages specifically numerous links page_c.php (an example). When I go to page_c, then hit the back button in my browser... IE 5.0 comes up and says:

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 button

.... and of course, if I hit Refresh it asks me whether or not I want to do it, then goes ahead and loads the page.

But surely there has to be someway to keep from having to do this? I've looked all over IE's options, including setting my security zone to custom/turning everything off etc. All to no avail! Any suggestions anyone?

Anon

Heh, whoops. I guess my only option is to use the 'GET' method instead of 'POST'. Ah well, ugly url's aside - it works.

Thanks!

[deleted]

Cache is a wonderfull thing, but I wish someday it would be fixed to actually work too...

trevordevore

I am pretty sure this has to do with the headers that are being sent with your pages. PHP generated pages don't send 'expires', cache-control', 'last-modified' or 'content-length' unless you are using sessions. If you are using Sessions then in the php.ini file will have the following entry:
session.cache_limiter = nocache. This means that PHP is sending headers that tell the browser not to cache the page, thus you have to reload it each time.
This can also be set to private or public which will send some of the required headers so that your page will not need to be refreshed each time.

If you aren't using sessions then you should send the proper headers yourself by doing the following before any output is sent to the browser (I've just thrown in some example numbers):

/
**This is the offset in seconds. Currently set to 3 days
/
$cache = 60 60 24 3;
/ Create the Expires header. */
$expires = "Expires: " . gmdate( "D, d M Y H:i:s", time() + $cache ) . " GMT";

/ Create the Cache-Control header. /
$cacheControl = "Cache-Control: max-age=" . 600 . ", must-revalidate"; /600 is ten minutes /

/ Create the last-modifed header/
$lastModified = "Last-Modified: ". gmdate( "D, d M Y H:i:s", @filemtime(PUTYOURFILEHERE) ) . " GMT";

/ Send the headers before any output /
header($expires);
header($cacheControl);
header($lastModified);

If you are using output buffering you can also send the content-length header.

Do not send headers if you are using sessions as PHP sends it's own headers when sessions are being used.

To check what headers my pages are sending out I do the following when logged into my user account via telnet:
username% telnet www.yourdomain.com 80
--hit enter
--type in:
HEAD / HTTP/1.0
or
HEAD /path/to/page/jobs.html HTTP/1.0
etc
--hit enter twice and you should see the head elements.

You can also check to see if your caching headers are correct by going to:
http://www.web-caching.com/cacheability.html

Hope this helps,

Trevor DeVore
Blue Mango Multimedia

Anon

I am adding this comment months after the original message just in case someone is doing a search for this very problem. Because there is a perfect solution that is not mentioned here.

When you use PHP's sessions, you get "page expired" errors when using the back button because PHP's session management sends out a "nocache" header. You can change that header to instead send "private" or "public" and suddenly your back button will again. However, your pages will be outdated -- never grabbing fresh data, always showing the same listing. To solve this, you want to completely BLANK OUT the header. How do you do this? In php.ini, make the session.cache_limiter look like this:

session.cache_limiter = ;

That's right, no value. You do this, and viola, the cache control returns to "at the browser's discretion" -- which means, you always get fresh data, and you never see a "page expired" warning. Yay.

Anon

Yes, the previous thread is true, BUT it comes with some Netscape issues (what doesn't?).

If you are using DHTML (<div>'s) that are hidden on the load of your document and then become visible with a JavaScript onMouseOver, Netscape likes to intermittently decide to display these <div>'s inaccurately on the load of the document.

To get around this, Netscape needs a no-cache header in order to not show the <div>'s until the appropriate time. You can either sniff the user's browser and write the header for Netscape user's only OR just put the following META tags at the top of your document.

IE will pretty much ignore them.

I hope this helps...