如何限制域名访问？白名单机制

                                   

    $whriteList = [
                                'a.xxxx.cn',
                                'b.xxxx.cn'                                 
    ];
    $domian = $_SERVER['HTTP_HOST']; 
                                //trim($_SERVER['SERVER_NAME'])                                 
                                //$domian=$_SERVER[ "HTTP_HOST"]                                    
                                if(!in_array($domian,$whriteList))
    {
                                return                                      403;
    }
?>