Laravel语法错误：T_PAAMAYIM_NEKUDOTAYIM

Question

我有一个在localhost上运行更好的网站，但是当我上传到在线服务器时，这会显示很多错误，例如：

  

语法错误，index.php第80行中出现意外的T_PAAMAYIM_NEKUDOTAYIM：

Index.php第80行

        // becomes global. can be access on any page
            $csrf_token = $csrf :: $token; 

Csrf.php

    <?php
    /**
     *  Csrf - Cross Site Request Forgery
     * @category  Security
     */
    class Csrf{
        public static $token=null;
        function __construct(){
            $token=get_session('csrf_token');
            if(empty($token)){
                $token=md5(random_str(12));
                set_session('csrf_token',$token);       //set new token in session if not available
            }
            self :: $token=$token;
        }

        /**
         *  Csrf - Verify if the request is coming from our origin
         * @category  Security
         */
        public static function cross_check(){
            $current_token=get_session('csrf_token');

            $req_token = "";
            if(!empty($_SERVER['HTTP_X_CSRF_TOKEN'])){
                $req_token=$_SERVER['HTTP_X_CSRF_TOKEN'];
            }
            elseif(!empty($_REQUEST['csrf_token'])){
                $req_token=$_REQUEST['csrf_token'];
            }

            if($req_token != $current_token){
                render_error("Cross-Site request Forgery Detected. Please Contact The System Administrator For More Information",403);
                exit;
            }

            return null;
        }
    }

请帮我解决。谢谢你。