Get data from cookie on subdomain with Codeigniter

I already checked couple threads here but I was not able fix my problem.

I have 2 apps:

• 1st app is pure php ecommerce website on domain www.mydomain.com, where I did initialization with:
  

Code:

session_set_cookie_params( $currentCookieParams["lifetime"], $currentCookieParams["path"], $rootDomain, // $rootDomain = ".mydomain.com" $currentCookieParams["secure"], $currentCookieParams["httponly"] );

• 2nd app uses Codeigniter on domain sub.mydomain.com and is configured like this:
  

Code:

$config['sess_driver'] = 'files'; $config['sess_cookie_name'] = 'cookie_name'; $config['sess_expiration'] = 7200; $config['sess_save_path'] = NULL; $config['sess_match_ip'] = FALSE; $config['sess_time_to_update'] = 300; $config['sess_regenerate_destroy'] = FALSE; $config['cookie_prefix'] = ''; $config['cookie_domain'] = '.mydomain.com'; $config['cookie_path'] = '/'; $config['cookie_secure'] = FALSE; $config['cookie_httponly'] = FALSE;

I will add an item to cart on www.mydomain.com. Data are stored in cookies under

Code:

cookie_name

. Then I open sub.mydomain.com to check if data are shared. In chrome dev tools under Application/Cookies I can see that value of

Code:

cookie_name

is same on both domains.
Problem is I am not able to get this data on subdomain with Codeigniter (using

Code:

$_SESSION

or

Code:

$this->session->userdata();

). It returns array with only item

Code:

[__ci_last_regenerate]

.
I created sample file on sub.mydomain.com/test.php where I am able to get data from session using php without codeigniter => so data are available there...But I need to get them with Codeigniter. Any ideas?