[Solved] Session issue : Can't keep it persistent

Hello,

I don't know why but I lose my session at any refresh.
I try to store it by file and now in my database.

Here it's the only thing I have when i refresh my page (anytime different) :

PHP Code:

Array
(
    [__ci_last_regenerate] => 1481814234
) 


This is my current config :

AUTOLOAD

PHP Code:

$autoload['libraries'] = array( 'database', 'session' ); 


CONFIG

PHP Code:

$config['sess_driver'] = 'database';
$config['sess_cookie_name'] = 'ci_sessions';
$config['sess_expiration'] = 0;
$config['sess_save_path'] = NULL;
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 30000;
$config['sess_regenerate_destroy'] = TRUE;

$config['sess_use_database'] = TRUE;
$config['sess_table_name'] = 'ci_sessions';


$config['global_xss_filtering'] = TRUE; 


MODEL

PHP Code:

public function createSession(){
        if( !isset( $this->session->watch_dog ) ){
            $this->session->set_userdata( 'watch_dog', 0);
        }
        if( get_cookie('watch_dog') == null ){
            set_cookie('watch_dog', 0,'130000');
        }
    }

    public function addConnectionCounterAttempt(){
        $this->createSession();
        // SESSION
        $new_value = $this->session->userdata['watch_dog'] + 1;
        $this->session->set_userdata( 'watch_dog', $new_value );
        // COOKIE
        set_cookie( 'watch_dog', $new_value, '3600' );
    } 


If you have any ideas...
Thank you.