Clearing cache on Back button?

Anon

I've got the users uploading an image, before committing this image to the server they can preview what it will look like, but if they select "Go Back" to edit their selection, upon returning to the view page, the old image is still displayed. Obviously the browser is reading the cache but how can I clear the cache? I tried using:

print("<META HTTP-EQUIV=\"Cache-control\" CONTENT=\"no-cache\"> \n");
and
print("<META HTTP-EQUIV=\"Pragma\" CONTENT=\"no-cache\"> \n");

but still with the same results. Any help would be appreciated.

Thanks,
Marcel.

Anon

I just wanted to add that with the picture the users are submitting a textual description that I would prefer not to clear...so the problem is a little more complex...How do I clear the cache of the image, but not the text? Or can I even?

Thanks again,
Marcel.

Anon

Hi there,

this might help....

On all the pages i run, I call a function like so

cache_control(900);

Where 900 is the time in secs for the page to be cached. Setting it to 0 wont cache it. This has worked wonders for me.

Cache_control was found in the comments section of http://www.php.net/manual/function.header.php
so I am not the author.

function cache_control($maxage=0) {
$Modified = "Last-modified: ".gmdate("D, d M Y H:i:s", time())." GMT";
$Expires = "Expires: ".gmdate("D, d M Y H:i:s", time() + $maxage)." GMT";
$CacheControl = "Cache-Control: must-revalidate, max-age=".$maxage.", ";
$CacheControl.= "s-max-age=".$maxage;
Header($CacheControl);
Header($Modified);
Header($Expires);
}

Remember, you have to call the function before anything is outputtet to the browser.

Good luck,
Jens

Anon

Thank you very much, I'll give it a go. I believe this will do what I need.

Marcel.

Anon

Hi,

I've been looking for info on this as well, however, in a slightly different manner. I have a simple form that updates a database, using a generated (auto-incremented) ID that's passed into the page.

If the user submits the page, and clicks back, they can essentially insert another record with the same info and same ID, which I don't want.

I tried using these cache control headers but the back button still produces the same page - I wish the page to refresh the database contents if the back button is pressed, i.e., just reload the page. Is this possible?

Thanks,
David

m_henry

If you move the auto_increment code to the header of the page you can control the count and then perhaps pass the info back for a comparison. Buyt yes it can be done, maybe not as easily as you would like but with some code wrestling you can do it.

Hope this helps....by the way, cach_control worked for me.(?)

saltwater

use MySQL's auto_increment