Imprima todas as sessões no Codeigniter
print_r($this->session->userdata);
or
print_r($this->session->all_userdata());
Super Skipper
print_r($this->session->userdata);
or
print_r($this->session->all_userdata());
$this->session->set_userdata('some_name', 'some_value');
$this->load->library('session');