Codeigniter $this->session->set_userdata() not working properly

i am generating a session but when i generate it i am not getting __ci_last_regenerate after calling $this->session->set_userdata('sessionName',$sessionArray) function. when i redirect after generate my session without __ci_last_regenerate the session data is not appearing on next page.i am using CI 3.1.4

$user_basic = array( 
    'user_id' => $user_id, 
    'email' => $this->input->post('email'), 
    'is_user_login' => 'true', 
    'language' => 'eng' 
); 
$this->session->set_userdata('user_basic',$user_basic); 

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

Thank you