php session_start();

[eluser]slowgary[/eluser]
I seem to remember reading that normal PHP sessions CodeIgniter do not get along very well. I could be wrong, but either way I'd recommend using the CodeIgniter session class instead. You really should never have to call session_start().

Code:

$this->load->library('session');

//to set some data
$this->session->set_userdata('your_field');

//to retrieve
$this->session->userdata('your_field');

Plus CI's session class makes storing sessions in the database very easy, so your apps can be more secure.