echo '<pre>';
print_r($this->session->all_userdata()); exit;

Array
(
    [__ci_last_regenerate] => 1462123135
    [uniq_session_id] => 6bcd0f6a162a5d17cbdc8a884aa510f7
)

Array
(
    [__ci_last_regenerate] => 1462123073
)