Urgent Help Need - same function inside function but create array for their values

Hi,

I am trying to create a function which will be able to fetch record from the database but the problem is the data is to be arrange in tree form. Means I to arrange my categories like below:

1) Computers
-----2)Laptops
-----3)Keyboards
4) Mobiles
-----5)Samsung
-----6)Sony

Now assume the bullet numbering of these categories as their id in database and parent id of 1 and 4 number is null but of 2, 3, 5 and 6 as their above.

Function I am using is below:

  function CategoryForListItem($parent_id = "") {
      $sql = empty($parent_id) ? "SELECT cat_id, cat_name, cat_level FROM category WHERE cat_parent_id IS NULL" : "SELECT cat_id, cat_name, cat_level FROM category WHERE cat_parent_id='$parent_id'";
      $result = mysql_query($sql);
      while($row = mysql_fetch_array($result)) {
        $category_list_array[] = array($row['cat_name'],$row['cat_id']);
        CategoryForListItem($row['cat_id']); //calling same function 
      }
    return $category_list_array;
  }

Code (markup):

This Function Returns:
It only returns the values from first while loop that is only return two loops, first is array("Computers", 1) and second is array("Mobiles", 4) . Like this

[COLOR="red"]array( [COLOR="darkgreen"]array("Computers",1)[/COLOR] ,  [COLOR="blue"]array("Mobiles", 4)[/COLOR] )[/COLOR]

Code (markup):

My Aim To Get:
I want an array from this function and array is multidimensional array with all categories values with their id as given below:

[COLOR="red"]array( [COLOR="green"]array("Computers",1)[/COLOR], [COLOR="darkorange"]array("Laptops",2)[/COLOR], [COLOR="blue"]array("Keyboards",3)[/COLOR] , and so on arrays...)[/COLOR]

Code (markup):

Thanks in Advance.
Please help me as it is urgent.

 

 
function CategoryForListItem($parent_id = "") {
      $sql = "SELECT cat_id, cat_name, cat_level FROM category";
      $result = mysql_query($sql);
      while($row = mysql_fetch_array($result)) {
        $category_list_array[] = array($row['cat_name'],$row['cat_id']);       
      }
    return $category_list_array;
  }

Code (markup):

I think this should work since you're category is determined if its a parent category if the cat_parent_id is null or if its a sub-category if the cat_parent_id has a value.