This question is a continuation of a previous question I asked, found
at https://answers.google.com/answers/main?cmd=threadview&id=123489. 
I was looking for a way to display PDF files in a browser window while
storing the PDF files outside the webserver's document root directory,
and the PHP code seen in the question's answer works.  The code looks
like this:

<?php
$file = "/var/docs/pdftest.pdf";
$filename = "pdftest.pdf";

header("Cache-control: private");
header("Content-Type: application/$ext");
header("Content-Length: ".filesize($file));
header("Content-Disposition: inline; filename=$filename");

readfile($file);
?>

Now my question is this: I've enabled SSL on my Apache webserver,
which works fine, but when I request a PDF download I get a warning
that the file I've requested contains insecure items.  I think it must
be a problem with the headers I'm sending, because if I move the file
into the document root and request it directly it works fine --
Acrobat Reader opens in the browser window and no SSL warnings appear.

So, to sum up: how do I need to modify the PHP code above to make it
SSL-safe?