Incompatible with Apple Devices

[Parrot]

I've set up code to allow users to purchase mp3 files. I keep the files in a non web-accessible directory and use a script that verifies that the user is logged in and has purchased the file before it lets them download it. Once the user has been validated it outputs the header specifying a file transfer and sends the file.

The problem is that iPhone and iPad users are complaining that their devices won't download the file. It works for everybody else.

Is there a fix for this? Some alternate way of doing this that would work on an Apple mobile device?

This is the relevant part of the code

if(file_exists($path))
{    
    header("Pragma: public");
    header("Expires: 0");
    header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
    header("Cache-Control: public");
    header("Content-Description: File Transfer");
    header("Content-Type: " . $mm_type);
    header("Content-Length: " .(string)(filesize($path)) );
    header('Content-Disposition: attachment; filename="'.basename($path).'"');
    header("Content-Transfer-Encoding: binary\n");
    
    readfile($path); // outputs the content of the file
}