codeigniter自定义会话表字段

I want to know if there is any way to define custom fields in the sessions table of CodeIgniter.

By default, CodeIgniter stores session values in the following fields:

`session_id`, 
`ip_address`, 
`user_agent`, 
`last_activity`, 
`user_data`

What if I want to store a little more information in the sessions table using cookies? I mean, if I want to add username and want to change the field name session_id to SessionID.

Is it possible to achieve that without too much effort??

You can use set_userdata() function

like this

    $newdata = array(
                'username'  => 'sudz',
               'email'     => 'sudz@some-site.com'                 
           );

    $this->session->set_userdata($newdata);

you can't change session_id its used by codeigniter, instead you can define your own session_id with defferent name. or you have to override the CI_Session class.