Request a file with a custom header

Question

I have an unusual requirement. Essentially I need a way so that, when the user clicks on a link or button, they will receive a PDF. The tricky part here is that the server w

Answer 1

Tested to work in chrome:

function toBinaryString(data) {
    var ret = [];
    var len = data.length;
    var byte;
    for (var i = 0; i < len; i++) { 
        byte=( data.charCodeAt(i) & 0xFF )>>> 0;
        ret.push( String.fromCharCode(byte) );
    }

    return ret.join('');
}


var xhr = new XMLHttpRequest;

xhr.open( "GET", "/test.pdf" ); //I had test.pdf this on my local server


xhr.addEventListener( "load", function(){
    var data = toBinaryString(this.responseText);
    data = "data:application/pdf;base64,"+btoa(data);
    document.location = data;
}, false);

xhr.setRequestHeader("magic", "header" );
xhr.overrideMimeType( "application/octet-stream; charset=x-user-defined;" );
xhr.send(null);

You can change application/pdf to application/octet-stream to have download prompt. But it's pretty easy to download from the chrome's reader as well.

In firefox nothing happens I guess it's because I don't have a plugin to deal with application/pdf installed. Changing to application/octet-stream will prompt a dl.

With IE I suppose you need some kind of VBScript/ActiveX hackery

If the file is huge, using data uri might crash the browser, in that case you can use BlobBuilder and Object URLs.

Answer 2

Instead of linking to the .PDF file, instead do something like

<a href="pdf_server.php?file=pdffilename">Download my eBook</a>

which outputs a custom header, opens the PDF (binary safe) and prints the data to the user's browser, then they can choose to save the PDF despite their browser settings. The pdf_server.php should look like this:

header("Content-Type: application/octet-stream");

$file = $_GET["file"] .".pdf";
header("Content-Disposition: attachment; filename=" . urlencode($file));   
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
header("Content-Description: File Transfer");            
header("Content-Length: " . filesize($file));
flush(); // this doesn't really matter.
$fp = fopen($file, "r");
while (!feof($fp))
{
    echo fread($fp, 65536);
    flush(); // this is essential for large downloads
} 
fclose($fp);

EDIT: The only way to add headers to a request from inside a browser (client-side) is use the XmlHttpRequest setRequestHeader method.

xhr.setRequestHeader('custom-header', 'value');