PHP file download simply spits out the buffer instead of the actual file

Question

First off, I understand this is not the best way of forcing a file download, it's hacky and it's horrible, but hey, I just get told what to do!

So I have a WP installation, and I'm trying to leverage using the WP AJAX to download a file.

My form hits an AJAX callback in functions.php, and after doing some bits n pieces, I am hitting this function:

function download_file()
{
    $file = get_template_directory()."/a_pdf_file.pdf";

    if(file_exists($file)) {

        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename="'.basename($file).'"');
        header('Expires: 0');
        header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
        header('Pragma: public');
        header('Content-Length: ' . filesize($file));
        ob_clean();
        flush();
        readfile($file);
        exit;
    }
    else
    {
        die('The provided file path is not valid.');
    }
}

The problem is, the buffer is just being spat out in the AJAX response. No file is being downloaded.

Do I need to do something on the AJAX end, in the success callback maybe?

The other options I have tried seem to fail too.

header('Location: $file_url'); doesn't work
tried all manner of header options, still no difference
window.open(url, '_blank') in AJAX callback gets blocked as a popup
window.location() opens in same window, not acceptable

*"`header('Location: $file_url');` doesn't work"* - Because; variables don't get parsed in single quotes. — Funk Forty Niner, Apr 05 '17 at 15:49
there's also no ajax/js here or how the `download_file()` function gets called. — Funk Forty Niner, Apr 05 '17 at 15:51
Possible duplicate of [Download file through an ajax call php](http://stackoverflow.com/questions/6668776/download-file-through-an-ajax-call-php) — Matt S, Apr 05 '17 at 15:53
@clearshot66 `header("Location: $file_url");` will work just as well; no need for extra characters/quotes. — Funk Forty Niner, Apr 05 '17 at 15:54
Ignoring the single/double quote problem, it didn't work either way. — Mr Pablo, Apr 05 '17 at 16:04

score 0 · Answer 1 · answered Apr 05 '17 at 15:59

Ajax can not directly download a file, instead you need to open it in it's own frame. You can create your own invisible iframe on the fly like this if you use jquery. This is from my code, but getting rid of jquery here should not be that hard.

function downloadUrl(url) {
    var iframe = document.createElement("iframe");
    iframe.src = url;
    $(iframe).hide();
    document.body.appendChild(iframe);
    $(iframe).load(function() {
        //Show error, if call returned an error instead of a file
        var cont = $(iframe).contents().find("body");
        if (cont.text().length != 0)
            alert(cont.text()); 
    });
}

PHP file download simply spits out the buffer instead of the actual file

1 Answers1