[PHP] Correct headers for I.E. to open PDF?

[Paul Danko]

I have searched the net, and found tons of developers with different
solutions to this problem, none of which I have found to work. 
 
What should the headers be for a client to download a PDF document and
have it open using adobe i.e. pluggin??
 
Here is code I am using, it works on some versions of I.E., but not all:
 
 
$pdfdoc = $__BASE_PDF_BUILD_DIRECTORY.$_GET['FID'];
            
$filesize = filesize($pdfdoc);
header("Pragma: ");
header("Expires: 0"); 
header("Cache-Control: must-revalidate, post-check=0,pre-check=0");
header("Content-type: application/pdf");
header("Content-Length: ".$filesize);
header("Content-Disposition: inline; filename=FILE.pdf");
header("Content-Transfer-Encoding: binary");
header("Accept-Ranges: bytes");
            
readfile($pdfdoc);
exit();
 
 
Why isn't it working?
 
Thanks,
 
-Paul