How to get controller method parameters in codeigniter?

I have implemented a controller to give access of data of candidates.

class List_Controller extends CI_Controller {
     public function __construct()
     {
         parent::__construct();
         $data[]=array();

         /*
         Here I want to get value of $area parameter, to save into logs
        */
         $userId=$this->session->userdata('userId'); 
         // save logs 
         $this->UrlAccessHistory->save($this->router->class,$this->router->method,$userId,"Web Application");

     }

    public function fetchList($area=null){
        // fetch list of records from specified area 
    }
}

$this->router->className gives name of controller Class and $this->router->method gives name of of function called.

Please help to get the list of parameters at location (see comments in code) in the constructor, so that I can store it in the logs.