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Avoid image caching after file upload
Posted on 2008-09-29
Hi,
I have multiple upload form on the same page to allow the user to upload images. On postback I process the image uploaded and display it as a thumbnail just beside the correspondant upload form. The problem is that the image displayed is not the new one but the old one (probably get from cache).
If I upload a new picture that doesnt exists on the system, I see it immediatly.
Same thing if a delete one of the picture, it disappeared immediatly.
The problem came when I overwrite an existent picture.
I tried bunch of things like :
<meta http-equiv="Expires" content="Wed, 26 Feb 1997 08:21:57 GMT">
<meta http-equiv="Pragma" content="no-cache">
or in php :
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// HTTP/1.1
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
// HTTP/1.0
header("Pragma: no-cache");
Please see the attach files, one is the html result, the other the php code to understand the logic of my page.
Thanks a lot!
example.txt
phpcode.txt
I have multiple upload form on the same page to allow the user to upload images. On postback I process the image uploaded and display it as a thumbnail just beside the correspondant upload form. The problem is that the image displayed is not the new one but the old one (probably get from cache).
If I upload a new picture that doesnt exists on the system, I see it immediatly.
Same thing if a delete one of the picture, it disappeared immediatly.
The problem came when I overwrite an existent picture.
I tried bunch of things like :
<meta http-equiv="Expires" content="Wed, 26 Feb 1997 08:21:57 GMT">
<meta http-equiv="Pragma" content="no-cache">
or in php :
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// HTTP/1.1
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
// HTTP/1.0
header("Pragma: no-cache");
Please see the attach files, one is the html result, the other the php code to understand the logic of my page.
Thanks a lot!
example.txt
phpcode.txt
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2
3 Comments
You may have to use sessions to to set a session to force the browser to a new session each time they go, and thus make the browser get the page from the server instead of the cache
PHP Code:
<?php
session_start();
$_SESSION = array();
session_destroy();
?>
Try that at the very top of the PHP page, see what happens. You are trying to force the browser to get the new image from the server EVERY time.
PHP Code:
<?php
session_start();
$_SESSION = array();
session_destroy();
?>
Try that at the very top of the PHP page, see what happens. You are trying to force the browser to get the new image from the server EVERY time.
Ok but what if I dont want to destroy my session. In need some info that are stored in $_SESSION.
I tried session_regenerate_id() just in case.. without success
Any other idea ?
I tried session_regenerate_id() just in case.. without success
Any other idea ?
you didn't say you had an active PHP session -- had you said so, it would have saved a lot of time.
http://us3.php.net/session_cache_limiter
http://us.php.net/header
http://www.webmasterworld.com/forum88/1003.htm
http://www.usenet-forums.com/archive/index.php/t-20949.html
http://php.oregonstate.edu/manual/en/function.session-cache-expire.php
You will find generally that a cache clear, clears the sessions too, but there are ways around this.
http://us3.php.net/session_cache_limiter
http://us.php.net/header
http://www.webmasterworld.com/forum88/1003.htm
http://www.usenet-forums.com/archive/index.php/t-20949.html
http://php.oregonstate.edu/manual/en/function.session-cache-expire.php
You will find generally that a cache clear, clears the sessions too, but there are ways around this.
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