Problem with downloading files with Internet Explorer over HTTPS

This behaviour has bitten me before. Yesterday I was asked to resolve the issue again. And as my memory is short I was again forced to search the web for a solution. The solution is simple – but also stupid.

The problem is that Internet Explorer does not handle file dowloads without caching over https very well. Or at all. According to knowledge articles on Microsofts website the problem occurs when having one or two of the http headers:

Pragma: no-cache
Cache-control: no-cache,max-age=0,must-revalidate

Previously I have have just omitted the http header “Pragma: nocache” for IE but it seems it does not always help.

So, whether you want it or not, the solution to the IE https download cache problem is to tell IE to cache the file.

if ((isset($_SERVER["HTTPS"]) && strtolower($_SERVER["HTTPS"] == "on")) &&
    preg_match("/MSIE/", $_SERVER["HTTP_USER_AGENT"])) {
	header('Pragma: cache');
} else {
	header('Pragma: no-cache');
}