php - What is user_data in CodeIgniter session used to? -

when in codeigniter run var_dump($this->session->all_userdata()); prints

array (size=5)   'session_id' => string '3403084ad9f5e2582a8d9269ceb68fb7' (length=32)   'ip_address' => string '127.0.0.1' (length=9)   'user_agent' => string 'mozilla/5.0 (compatible; msie 10.0; windows nt 6.1; trident/6.0)' (length=64)   'last_activity' => int 1365456079   'user_data' => string '' (length=0) 

since these automatically filled in values ci, i'm wondering if could/should overwrite user_data index, e.g 'user_data' => $username.

if ci keep update index, not work. must store session-data own indexes. experience on ci knows fixed index in session array used for. there no documentation it.

the user_data field used session params

once want put session value use do:

$this->session->set_userdata('x','y'); 

the userdata('x') stored in user_data array key of session y value

so user_data key in session (or somenthing similar :d ):

'user_data' => ['x'=>'y'] 

so ,yes , overwrite value of user_data, setting session value need/want

more user_data field doc seems db field ci uses store session params: http://ellislab.com/codeigniter/user-guide/libraries/sessions.html

in system7libraries/session.php there no big trace of user_data these lines:

// run update query         $this->ci->db->where('session_id', $this->userdata['session_id']);         $this->ci->db->update($this->sess_table_name, array('last_activity' => $this->userdata['last_activity'], 'user_data' => $custom_userdata)); 

which seems updating db field called user_data (seems) related session db