d盾能查php后门那,这个php文件用D盾扫出来是已知后门，怎么看得出那句是后门...

//运行目录

define("FCPATH", str_replace("\\", "/", dirname(__FILE__)));

//加载核心类

require_once FCPATH.'/include/class.main.php';

//加载配置文件

require_once FCPATH . '/save/config.php';

define("ROOT_PATH", $CONFIG["ROOT_PATH"]? $CONFIG["ROOT_PATH"] : GlobalBase::is_root());

//输出json格式文件

header('content-type:application/json;charset=utf8'); //header("Content-Disposition:attachment;filename='json.js'");

//循环取传入参数，支持POST和GET

foreach ($_REQUEST as $k => $v) {

$$k = trim(urldecode($v));

}

//参数初始化

$cb = isset($cb) && $cb ? $cb : '';

$tp = isset($tp) && $tp ? $tp : '';

$url = isset($url) && $url ? $url : '';

$wd = isset($wd) && $wd ? $wd : '';

$line = isset($line) && $line ? $line : '0';

$id = isset($id) ? $id : '';

$flag = isset($flag) ? $flag : '';

$app = isset($app) ? $app : 'xysoft';

$dd = isset($dd) && $dd ? $dd : 0;

$loadjs = isset($loadjs) ? $loadjs : 0;

//全局变量,输出信息

$info = array('success' => 0, 'code' => 0);

//公用函数,API接口

if ($tp == 'getnum') {

echo sizeof($jx_url);

exit;

}

if ($tp == 'set') {

setcookie("url_num", $line, time() + 3600 * timecookie);

exit;

}

if ($tp == 'getset') {

exit(isset($_COOKIE["url_num"]) ? $_COOKIE["url_num"] : '0');

}

//全局变量,读写缓存

$cache = new Main_Cache(array("cachetype" => $CONFIG["chche_config"]["type"], "cacheDir" => "./cache", "cacheprot" => $CONFIG["chche_config"]["prot"], 'cacheTime' => GlobalBase::is_time($CONFIG["chche_config"]["time"])));

//加载防火墙规则

Blacklist::parse($CONFIG["BLACKLIST"]);

switch ($tp) {

//取配置参数及线路列表

case 'getparm' :

require_once FCPATH . '/save/yun.data.php';

$info['success'] = 1;

$info['type'] = 'getparm';

$info['app'] = server::lsUserAgen($CONFIG["play"]['all']['AppName']);

$CONFIG["play"]['define']['jx_link'] = $CONFIG["jx_link"];

$CONFIG["play"]['define']['jx_url'] = $CONFIG["jx_url"];

$CONFIG["play"]['define']['live_url'] = $CONFIG["live_url"];

$CONFIG["play"]['define']['jx_link'] = $CONFIG["jx_link"];

$CONFIG["play"]['define']['url_jmp'] = $YUN_DATA["url_jmp"];

$CONFIG["play"]['define']['timeout'] = $CONFIG["timeout"];

我来回答