Using existing session data from a non-CI website in a CodeIgniter website

Update: I tried changing $config['sess_expiration'] = 7200; to $config['sess_expiration'] = 0;

and $config['cookie_prefix'] = ''; to $config['cookie_prefix'] = 'myprefix'; but that didn't help.


All I see on my CI page which has Print_r($_SESSION):

PHP Code:

Array
(
    [__ci_last_regenerate] => 1506167810
) 


Where as plain.php shows me all the session data.

Codeigniter change the save path of the session. it is not the same as the default from php.