getting property of non-object error

Everything in a session is only for "this" user, so "userdata()" is not a special place where data is stored.
$this->session->userdata() is only for backwards compatibility.
In previous versions of CI, you had to add data to the session like this:

PHP Code:

$this->session->set_userdata('some_name', 'some_value'); 


But from version 3.x you can do this:

PHP Code:

$this->session->some_name = some_value; 


or even:

PHP Code:

$_SESSION['some_name'] = some_value; 


To retrieve data from the session, you can do the same thing:

PHP Code:

$some_name = $this->session->userdata( 'some_name');
$some_name = $this->session->some_name;  //this is called the magic getter!
$some_name = $_SESSION['some_name']; 


all do the same.

It's explained here: https://www.codeigniter.com/userguide3/l...ssion-data