CodeIgniter Session Destratide automáticamente después de la redirección

//if you are working in CI 3.x and 
//just upgraded your server php version to php 7.x

//Go to system/libraries/Session/session.php search for and replace 
ini_set('session.name', $params['cookie_name']); 
//by 
ini_set('session.id', $params['cookie_name']);
hansal