help needed about logic.

[eluser]demiRon[/eluser]
Hi;
i'm try to build new app. News Portal.

i want to make a class which is complete solution for site navigation.

i mean:

segments -> http:/xxxxx. com/content/maincategory/subcategory
Contents related with subcategory.

Code:

class Content extends Controller
{
function __construct()
{
  parent::Controller();
}

function index()
{
  // this is Main Category calls first SubCategory
  //some data array
  $this->parser->parse('theme/'.$theme.'/cont', $data);
}

function subcat($subcat)
{
  //some data array $subcat
  $this->parser->parse('theme/'.$theme.'/cont', $data);
}

}

Now; i get this values; but i want to get these values at begin.
i tried to move these in __constructor but i get many errors like "unexpected T_VARIABLE"

Code:

$cat  =$this->uri->segment(2, 0);
$acat =$this->uri->segment(3, 0);

Ps: sorry for my bad eng.