PHP 强制下载类型

function downloadFile($file){
/*Coded by Alessio Delmonti*/        
        $file_name = $file;
        $mime = 'application/force-download';
        header('Pragma: public');       // required
        header('Expires: 0');           // no cache
        header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
        header('Cache-Control: private',false);
        header('Content-Type: '.$mime);
        header('Content-Disposition: attachment; filename="'.basename($file_name).'"');
        header('Content-Transfer-Encoding: binary');
        header('Connection: close');
        readfile($file_name);           // push it out
        exit();
}