I have a problem converting data retrieved from MySQL database into an xml format using php.

The xml file is used to build a navigation menu. This menu has 2 parts: a list of categories and their subcategories.

This is how the XML file should look:

http://www.corecreations.co.za/nav_menu/cat_menu.xml

Below is the structure of the database. I have two tables: category_tbl and subcategory_tbl.

category_tbl has three fields: cat_id, cat_name and cat_location
subcategory has three fields too: subcat_id, subcat_name and cat_id (foreign key)

Link to database setup:

http://www.corecreations.co.za/nav_menu/menu_db.sql

Please create the database menu_db and then import the tables and values.

The problem I am faced with is adding all subcategories, with the same cat_id, to the correct category. All the subcategories with cat_id = cat0001 should all be child nodes of category cat0001 i.e.

<cat_item cat_id = "cat0001">
<subcat_item cat_id = "cat0001" subcat_id = "subcat0001"/>
<subcat_item cat_id = "cat0001" subcat_id = "subcat0002"/>
<subcat_item cat_id = "cat0001" subcat_id = "subcat0003"/>
</cat_item>

I have tried for a while and now seek help if anyone can get this right.
Here is the php file, all I can get is link the first category with its subcategories.

PHP File: http://www.corecreations.co.za/nav_menu/menu.php
Thanks in advance.

Core Creations