How to use constructor in Codeigniter?

 Use constructor in Codeigniter

class Welcome extends CI_Controller {

/**

* Index Page for this controller.

*

* Maps to the following URL

* http://example.com/index.php/welcome

* - or -

* http://example.com/index.php/welcome/index

* - or -

* Since this controller is set as the default controller in

* config/routes.php, it's displayed at http://example.com/

*

* So any other public methods not prefixed with an underscore will

* map to /index.php/welcome/<method_name>

* @see https://codeigniter.com/user_guide/general/urls.html

*/

 public function __construct()

    {

        parent::__construct();

        $this->load->library('session');

        $this->load->helper('html');

        $this->load->helper('url');

        $this->load->helper('form');

        $this->load->helper('file');

        $this->load->library('form_validation');

        $this->load->model('Customer_model');

    }

}