Contents of PHP header content: The attachment forces the .php file or online

I want to download a single .mp3 file from my site but when using this code it forces a .php in Firefox and Safari. But in chrome it will send force the file as inline and play on the page. How can i get them to actually download a .mp3 file?

$track = $_SERVER['QUERY_STRING'];

if (file_exists("/home/user/gets/" .$track)) {
    header("Content-Type: audio/mpeg");
    header('Content-Length: ' . filesize($track));
    header('Content-Disposition: attachment; filename="test.mp3"');
    $str = "/home/user/gets/".$track;
    readfile($str);
    exit;
} else {
    header($_SERVER['SERVER_PROTOCOL'].' 404 Not Found', true, 404);
    echo "no file";
}

I have also tried to download a .zip file as well and changing the Content-Type to application/ocetet-stream but it forces .php files on all browsers.

//$track = $_SERVER['QUERY_STRING'];
$track = 'testfile.zip';
if (file_exists("/home/user/gets/" .$track)) {
    header("Content-Type: application/octet-stream");
    header('Content-Length: ' . filesize($track));
    header('Content-Disposition: attachment; filename="test.mp3"');
    $str = "/home/user/gets/".$track;
    readfile($str);
    exit;
} else {
    header($_SERVER['SERVER_PROTOCOL'].' 404 Not Found', true, 404);
    echo "no file";
}

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I think filesize($track) is wrong, it should be the whole path filesize("/home/user/gets/".$track). This would cause php to output error messages, preventing you from setting the content-length and disposition header.