$file   =   fopen($filename, "r ");
Header( "Content-type:   application/octet-stream ");
Header( "Accept-Ranges:   bytes ");
Header( "Accept-Length:".filesize($filename));
Header( "Content-Disposition:attachment;filename= ".$filename);
echo   fread($file,filesize($filename));
fclose($file);

function download_file($archivo, $downloadfilename = null) {
 
        if (file_exists($archivo)) {
            $downloadfilename = $downloadfilename !== null ? $downloadfilename : basename($archivo);
            header('Content-Description: File Transfer');
            header('Content-Type: application/octet-stream');
            header('Content-Disposition: attachment; filename=' . $downloadfilename);
            header('Content-Transfer-Encoding: binary');
            header('Expires: 0');
            header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
            header('Pragma: public');
            header('Content-Length: ' . filesize($archivo));
     
            ob_clean();
            flush();
            readfile($archivo);
            exit;
        }
     
    }