Download file not working

[adikat]

I am trying to set up a webpage where a user can download a .PNG image. The download works fine via computer and browser but it doesn't work when I try to download it via a browser on my Android phone. It tries to download but then give me 'download unsuccessful' it doesn't give any other errors.

Here is the PHP code that I am using:

 
header('Content-Description: File Transfer');
        header('Content-Type: image/png');
        header('Content-Disposition: attachment; filename=filename.png');
        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));
        ob_clean();
        flush();
        echo $file;
 

Any ideas?