is it possible not to cache an image?

[ainars]

I use a php script to generate images with random codes to avoid automatised form submissions. The script generates an image with random code and writes the code to MySQL. When user enters a correct code this code is being deleted from MySQL. It works for most users, but some users see the same code again and again. Is there some another way hot to prevent the image of being cached. Thats what I included in the script which generates the code:

Header("Content-type: image/png");
Header('Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0');
Header('Expires: Thu, 19 Nov 1981 08:52:00 GMT');
Header('Pragma: no-cache');

[Moharo]

hey ainars

I had exactly the same problem with image cache... this problem seems to persist mostly in Internet Explorer browsers, the header() function that you have would probably work for mozilla....

this is what i did to overcome this problem... i generated a file with a unique filename.... and that's it !!! meaning that the image filename was different each time it got generated... you may use php function uniqid() which generates a unique string based on time, additianally you can do rand() to make sure that the filenames are totally unique.....

<?php

$uniqid = uniqid("",false);
$filename = session_id() . "_" . $uniqid;

?>

have a look at www.php.net/uniqid

hope that helped you 😃