codeigniter session为什么gen auto？

Question

result $member form db I set

$sess['session_id']=$rs['user_id'];
$sess['session_name']=$rs['user_username'];
$this->session->set_userdata($sess);

my receive

$this->session->userdata('session_id') = 1
$this->session->userdata('user_username') = admin

but for a moment i see that

$this->session->userdata('session_id') = 700336412dd230af450558b92a728b59  

is wrong

$this->session->userdata('user_username') = admin

why session_id (num) change auto ?

THIS MY CONFIG config.php

$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 0;
$config['sess_expire_on_close'] = FALSE;
$config['sess_encrypt_cookie'] = FALSE;
$config['sess_use_database'] = FALSE;
$config['sess_table_name'] = 'ci_sessions';
$config['sess_match_ip'] = FALSE;
$config['sess_match_useragent'] = TRUE;
$config['sess_time_to_update']  = 300;

Answer 1

When you want to change session data use:

$this->session->set_userdata('session_name', $session_value);

When you want to get the session use:

$session_value = $this->session->userdata('session_name');

More details, read userguide

Also don't use variable name like: session_id