为什么下载的文件没有下载而是显示在浏览器中？

Question

I redirect the visitors in my website from page A to page B. In page BI expect users to get the downloaded PDF file (to be downloaded when page B is loading). I have taken the code from another article (see a previous question answered here ) and my code of page B is the following:

<?php
header('Content-Disposition: attachment; filename=nature.pdf');
header('Content-type: application/pdf'); 
$fn=fopen("/wp-content/nature.pdf","r");
fpassthru($fn);
?>

The output is not by opening a download dialog box, instead some unreadable characters are displayed in browser such as the following (I have just picked up a small sample below):

%PDF-1.4 % 3 0 obj <>stream x MK1 o + $zIg& V=T =Xo K i+#V yx3 ඀(BX pW`

Server: OS Linux; PHP version: 5.2.17

The visitor -> Browser: Firefox; OS: Windows 2000

Is it possible to fail due to the old OS on client side? If not, does anybody know a solution how to force the download? Any help would be highly appreciated.

Thanks.

Answer 1

Try it with the Content-Length header:

ob_clean(); ob_start();
header('Content-Disposition: attachment; filename=nature.pdf');
header('Content-type: application/pdf'); 
header ("Content-Length: ".filesize("/wp-content/nature.pdf"));
readfile("/wp-content/nature.pdf");
exit;

Answer 2

There was a quirk in the really old browsers when Content-disposition was first being introduced, some of the really old browsers wouldn't show the "Save As" dialogue unless it couldn't recognize the type of file you were trying to open. Try setting the Content-type to nothing (or something unrecognizable), and see if that'll force the older browser to pop the save-as dialogue.

header('Content-type: ');

If that works, then I'd suggest adding in a line of PHP to detect whether or not they're on an old browser before running that line, as modern browsers will use that header to determine what program the file should be opened with.