CodeIgniters session library - how to?

[eluser]v33s[/eluser]
Hello! Thanks a lot Seppo. That`s I need!

Code:

if (!$this->session->userdata('is_admin'))

Code:

array(
    'id' => $row->id,
    'username' => $this->input->post('username'),
    'is_admin' => true

So I understand it now! I must create a session with uniqe phrase like 'is_admin' and type it for TRUE. Next is to check if this session is TRUE and is set. But why I can not use something like that:

Code:

if(!isset($this->session->userdata('is_admin'))