Entry

How can I force a link to result in the user downloading a file?

Aug 28th, 2000 07:00
Jonathan Haase, Christian Schmidt, Nathan Wallace, Rasmus Lerdorf

If you just want to force a download use the header() function to set
the Content-type to be application/octet-stream.

http://www.php.net/manual/function.header.php3


Internet Explorer's MIME-type support is broken, so it does not react to
the above. However, if you in addition use the Content-Disposition
header you can also force MSIE 5 to download the file.

This header also allows you to specify a filename. This works in both
Netscape and MSIE 5.

header("Content-Disposition: attachment; filename=\"myfile.abc\"");

One item of note is that IE 5 will not download the file if the 
filetype is html or text.  IE will display the file in the browser 
rather than bringing up the file-save-as dialog.
 
I have found a way to "force" IE to bring up the file-save-as dialog.  
It seems that the problem with the above example is that IE 
uses "sniffing" to determine the mime type if you specify octet-
stream.  Even if you use the Content-Disposition header.  However 
Microsoft did put in a way to disallow this "sniffing". If you specify 
a mime type which is not immediately recognized, but which appears to 
be valid then IE will accept this mime-type without sniffing and handle 
the Content-Disposition header properly.  In my code I specified

header("Content-Type: application/force-download");
header("Content-Disposition: attachment; filename=\"myfile.abc\"");

This correctly forced IE to download the file instead of displaying it 
and still functions correctly in Netscape.