You can set data to session simply like this in Codeigniter:
$this->load->library('session');
$this->session->set_userdata(array(
'user_id' => $user->uid,
'username' => $user->username,
'groupid' => $user->groupid,
'date' => $user->date_cr,
'serial' => $user->serial,
'rec_id' => $user->rec_id,
'status' => TRUE
));
and you can get it like this:
$u_rec_id = $this->session->userdata('rec_id');
$serial = $this->session->userdata('serial');