Controller not recieving my parameter

[eluser]Joures[/eluser]
Yeah, ther is some code you're not seeing

Code:

<?php

class Subcategories extends Controller {
    
    public function display($id) {
        
     // fetching subcategories depending on $id
     $vars['categories'] = Doctrine_Query::create()
         ->select('s stuff')
         ->from('Stuff s')
         ->where('s.Parent_id = ?', $this->id)
         ->execute();
    }
}

I've tried your solutions, and it works, as long as i'm referencing $id alone, instead of $this->id. Any ideas as to why that is?