How to login with facebook in codeigniter?

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<?php
defined('BASEPATH') OR exit('No direct script access allowed');

use FacebookFacebook;

class FacebookLogin extends CI_Controller {

    public function __construct()
    {
        parent::__construct();
        require_once APPPATH.'third_party/facebook_sdk/autoload.php'; //Include Facebook SDK
        $this->load->library('session'); //Load CI session library
    }

    public function login()
    {
        $fb = new Facebook([
            'app_id' => 'YOUR_APP_ID',
            'app_secret' => 'YOUR_APP_SECRET',
            'default_graph_version' => 'v2.10',
        ]);

        $helper = $fb->getRedirectLoginHelper();

        $permissions = ['email']; // Optional permissions

        $loginUrl = $helper->getLoginUrl('http://yourwebsite.com/facebook/callback', $permissions);

        redirect($loginUrl);
    }

    public function callback()
    {
        $fb = new Facebook([
            'app_id' => 'YOUR_APP_ID',
            'app_secret' => 'YOUR_APP_SECRET',
            'default_graph_version' => 'v2.10',
        ]);

        $helper = $fb->getRedirectLoginHelper();

        try {
            $accessToken = $helper->getAccessToken();
        } catch(FacebookExceptionsFacebookResponseException $e) {
            // When Graph returns an error
            echo 'Graph returned an error: ' . $e->getMessage();
            exit;
        } catch(FacebookExceptionsFacebookSDKException $e) {
            // When validation fails or other local issues
            echo 'Facebook SDK returned an error: ' . $e->getMessage();
            exit;
        }

        if (! isset($accessToken)) {
            if ($helper->getError()) {
                header('HTTP/1.0 401 Unauthorized');
                echo "Error: " . $helper->getError() . "
";
                echo "Error Code: " . $helper->getErrorCode() . "
";
                echo "Error Reason: " . $helper->getErrorReason() . "
";
                echo "Error Description: " . $helper->getErrorDescription() . "
";
            } else {
                header('HTTP/1.0 400 Bad Request');
                echo 'Bad request';
            }
            exit;
        }

        // Logged in
        $oAuth2Client = $fb->getOAuth2Client();
        $tokenMetadata = $oAuth2Client->debugToken($accessToken);
        $tokenMetadata->validateAppId('YOUR_APP_ID');

        $longLivedAccessToken = $accessToken->getValue();

        $this->session->set_userdata('access_token', $longLivedAccessToken);

        redirect('your_dashboard_url');
    }
}