$this->load->library("session");
   $userdata = array(
    "user_id"  => $user_info["user_id"]
    , "name"   => $user_info["name"]
    , "email"   => $user_info["email"]
    , "logged_in" => true
    , "guest"  => ""
   );

$this->session->set_userdata($userdata);