How to force Chrome NOT to cache redirects?

Question

A simple HTML code:

image.php is a script that returns a random Redirect to a static image wi

Answer 1

From a link posted in another question:

 The first header Cache-Control: must-revalidate means that browser must send validation request every time even if there is already cache entry exists for this object.
Browser receives the content and stores it in the cache along with the last modified value.
Next time browser will send additional header:
If-Modified-Since: 15 Sep 2008 17:43:00 GMT

This header means that browser has cache entry that was last changed 17:43.
Then server will compare the time with last modified time of actual content and if it was changed server will send the whole updated object along with new Last-Modified value.

If there were no changes since the previous request then there will be short empty-body answer:
HTTP/1.x 304 Not Modified

You can use HTTP's etags and last modified dates to ensure that you're not sending the browser data it already has cached.

$last_modified_time = filemtime($file); 
$etag = md5_file($file); 

header("Last-Modified: ".gmdate("D, d M Y H:i:s", $last_modified_time)." GMT"); 
header("Etag: $etag"); 

if (@strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == $last_modified_time || 
    trim($_SERVER['HTTP_IF_NONE_MATCH']) == $etag) { 
    header("HTTP/1.1 304 Not Modified"); 
    exit; 
}