public function authenticate($username, $password){

        $loginQuery = "SELECT AdminID,Username,Password,AdminLevel,Lastlogin FROM adminusers WHERE username = ? AND password = ?";
        $stmt = $this->mysqli->prepare($loginQuery);
        $stmt->bind_param('ss', $username, $password);
        $stmt->execute();

        $stmt->store_result();

        $num_of_rows = $stmt->num_rows;

        $stmt->bind_result($AdminID, $username, $password,$AdminLevel,$Lastlogin);


            if($num_of_rows == 1){
                $this->username = $username;
                $this->password = $password;
                $this->authenticated = true;
            }

        $stmt->free_result();

    }