why my session lost in other pages?

Hi
it's first time that I use Codeigniter. after authentication for login I set session in Login_model.php:

PHP Code:

$data_session = array(
                'PersonId' => $PersonId,
                'PersonEmail' => $PersonEmail,
                'PersonName' => $PersonName,
                'PersonFamily' => $PersonFamily,
                'Login' => true);
            $this->session->set_userdata($data_session); 


  I can see my data by :

PHP Code:

print_r($this->session->userdata()); 


on Login_model.php file . they are some thing like this:

Code:

Array
(
  [__ci_last_regenerate] => 1510383844
  [PersonId] => 129
  [PersonEmail] => [email protected]
  [PersonName] => PersonName
  [PersonFamily] => PersonFamily
  [Login] => 1
)

but when I redirect to another page I can find them. my print_r result is this:

Code:

Array
(
  [__ci_last_regenerate] => 1510384212
)

my current setting:
config.php

PHP Code:

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'east';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = sys_get_temp_dir();
//$config['sess_save_path'] = 'ci_sessions';
$config['sess_match_ip'] = TRUE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE;
//------------------
$config['cookie_prefix']    = '';
$config['cookie_domain']    = 'http://domain.com/admin/';
$config['cookie_path']        = '/';
$config['cookie_secure']    = FALSE;
$config['cookie_httponly']     = FALSE; 


autoload.php

PHP Code:

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