Question

I have a table with three columns: id, ref and catName. Every row contains a category which can be a sub category; if so than the ref column references to the id of the main category. Off course this method makes sure you can create numerous sub categories.

Now I want to make a url for every category containing of the catName‘s of all its parents.

private function getCatUrl($cat, $ur = array()){
       $sql = "SELECT * FROM shop_cat WHERE id = :id LIMIT 1";
       $st = $this->db->prepare($sql);
       $st->bindParam('id', $cat, PDO::PARAM_INT);
       $st->execute();

       $rij = $st->Fetch();
       $ur[] = urlencode($rij['naam']);

       if($rij['ref'] == 0){
           //Done, I've reached the top parent;
           return implode('/',$ur);

       }else{
           //there is a parent/reference above this level
           //getting there
           $this->getCatUrl($rij['ref'], $ur);

       }

   }

Somehow this only produces a $ur for the top parent and not for the childs.
What am I doing wrong?

Sample of the database:

id  ref catName
1   0   GroundFloor
4   1   Portal
5   1   Stairs

2   0   FirstFloor
6   2   DiningArea
12  6   Chair
7   2   Toilet   
9   2   SittingRoom
10  9   Couch
11  9   Dresser

3   0   Roof
8   3   LoungeChair

Answer 1

You are doing it wrong.

I would recommend for you to look into Closure Tables [1] [2] [3], and also read the SQL Antipatterns book ( it covers the trees in second chapter).