login dan daftar menggunakan akun google pada codeigniter

 public function create_google(){
		// Include libraries google api php
		include_once APPPATH .'libraries/google-api-client/Google_Client.php';
		include_once APPPATH .'libraries/google-api-client/contrib/Google_Oauth2Service.php';

		// Disini di inputkan Google Project API Credentials
		$clientId = '#'; //client id ditulis disini
		$clientSecret = '#'; //client secret ditulis disini
		$redirectUrl = base_url() . 'v1/user/create_google/';

		//Call Google API
		$gClient = new Google_Client();
		$gClient->setApplicationName('Login');
		$gClient->setClientId($clientId);
		$gClient->setClientSecret($clientSecret);
		$gClient->setRedirectUri($redirectUrl);
		$google_oauthV2 = new Google_Oauth2Service($gClient);
		if(isset($_GET['code']))
		{
			$gClient->authenticate($_GET['code']);
			$_SESSION['token'] = $gClient->getAccessToken();
			header('Location: ' . filter_var($redirectUrl, FILTER_SANITIZE_URL));
		}
		if ($gClient->getAccessToken()) {
			$userProfile = $google_oauthV2->userinfo->get();
			$userData['oauth_provider'] = 'google';
			$userData['oauth_uid'] = $userProfile['id'];
			$userData['first_name'] = $userProfile['given_name'];
			$userData['last_name'] = $userProfile['family_name'];
			$userData['email'] = $userProfile['email'];
			//$userData['gender'] = $userProfile['gender'];
			$userData['locale'] = $userProfile['locale'];
			$userData['profile_url'] = $userProfile['link'];
			$userData['picture_url'] = $userProfile['picture'];

			$resp = $this->m_user->user_create_data($userData);
			if(!empty($resp)){
				$data['userData'] = $userData;
				$this->session->set_userdata('userData',$userData);
			} else {
			   $data['userData'] = array();
			}

			if($resp['errorCode']  == 200){
				 $stat = "SUCCESS";
			}else{
			  $stat = "ERROR";
			}
			$count = array($resp);
			$jsonAr = array(
				"_meta" => array('status' => $stat,'count' => count($count)),
				"result" => $resp
			);
			json_output($resp['errorCode'],$jsonAr);
		} else {
			$url = $gClient->createAuthUrl();
			header("Location: $url");
			exit;
		}
    }

saya dapet dari google script diatas , nah di sini saya mau buat fungsi daftar dan login pakai akun google, script di atas sudah mempunyyai fungsi login dan daftar nah cara penerapannya gmana ?? untuk function login dan daftar hanya 1 saja?