php下载代码在苹果无效，怎么解决？：报错

@ini_set("memory_limit","128M");
        //开始下载文件
        header('Content-Description: File Transfer');
        header('Content-Type: application/octet-stream');
 header('Content-Disposition: attachment; filename='.$name.'.'.$downInfo['ext']);
        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($file));
        ob_clean();
        flush();
        readfile($file);

这段代码在谷歌、安卓手机都能下载，苹果手机却不能下载了，怎么解决呀？