Sending file to a browser as attachment

Question

How to send a file to the browser as attachment if the meant file resides on a 3rd party server (without prior downloading or streaming)?

Solution 1

From another server without downloading to your server:

header('Location: http://thirdparty.com/file.ext');

Without downloading the file locally you have no authorization in the external server, so you have to tell the browser what to do, thus the redirect header, it will tell the server to go directly to the url provided, thus loading the download.

From your server you would do:

if (file_exists($file))
{
    if(false !== ($handler = fopen($file, 'r')))
    {
        header('Content-Description: File Transfer');
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename='.basename($file));
        header('Content-Transfer-Encoding: binary');
        header('Expires: 0');
        header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
        header('Pragma: public');
        header('Content-Length: ' . filesize($file)); //Remove

        //Send the content in chunks
        while(false !== ($chunk = fread($handler,4096)))
        {
            echo $chunk;
        }
    }
    exit;
}
echo "<h1>Content error</h1><p>The file does not exist!</p>";

Taken from another question I have answered

Solution 2

http://php.net/manual/en/function.header.php#example-3655

If you want the user to be prompted to save the data you are sending, such as a generated PDF file, you can use the » Content-Disposition header to supply a recommended filename and force the browser to display the save dialog.

<?php
// We'll be outputting a PDF
header('Content-type: application/pdf');

// It will be called downloaded.pdf
header('Content-Disposition: attachment; filename="downloaded.pdf"');

// The PDF source is in original.pdf
readfile('original.pdf');
?>

Comments

[mario]

There is no way to accomplish that. You have no influence over the handling of remote resources. And HTTP clients do not support message/external-body payloads.

[Gumbo]

Better use application/octet-stream.

[RobertPitt]

he did say without prior downloading or streaming.

[RobertPitt]

this would send a file stored locally, please re-read the question at hand.

[RobertPitt]

Not quite, using the redirect function will create the illusion that the file is being downloaded from his server.

[Sam Vloeberghs]

fopen requires 2 parameters, the second should be the mode, in this case "r" for read

[Asaelko]

fopen + fread by chunks isn't a good way — too slow. Use readfile($file) after headers for speed up.

[user3161924]

If you get corrupted file (space prefixed) you need to add ob_end_clean(); after the last header() function.