Forced download stopped working

I have a php script that I have used for years to force downloads from my website. But sometime in the last month or so, it stopped working and is triggering file not found errors. The weird thing is that in firefox, if I do view source on the error page, it is the file I was trying to download. And doing File > Save from there give you the correct file. So I know it's not a problem with the script not finding the file on the server.

Is there something wrong with how I am setting up the headers?

header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: private",false); 
header('Content-Type: application/octet-stream');
header('Content-Transfer-Encoding: Binary');
header('Content-length: '.filesize($file_url));
header('Content-disposition: attachment; filename="'.basename($file_url).'"')开发者_JAVA技巧;
readfile($file_url);

Can you try this function?

function force_download($file){
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename='.basename($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($file));
    readfile($file);
    exit;   
}

I ended up cheating to make this work.

header("Location: $file_url"); //file_url is now the real url, not the path

And then used cPanel to make sure all the MIME types I was using were set to application/octet-stream.