php 文件下载 出现下载文件内容乱码损坏的解决方法

public function download(){    $upload=M('upload');    $data=$upload->find($_GET['id']);    if(empty($data)){        header('HTTP/1.0 404 Not Found');        header('Location: .');    }else{    $path='./public/Uploads/'.$data['savename'];    header("Content-Type:".$data['type']);    header('Content-Disposition: attachment; filename="'.$data['name'].'"');    header('Content-Length:'.$data['size']);    ob_clean();    flush();    readfile($path);    }}

ob_clean();flush();