function buildCategoryOptions($catId = 0)
{
	$sql = "SELECT cat_id, cat_parent_id, cat_name
			FROM tbl_category
			ORDER BY cat_name";
	$result = dbQuery($sql) or die('Cannot get Product. ' . mysql_error());
	
	$categories = array();
	while($row = dbFetchArray($result)) {
		list($id, $parentId, $name) = $row;
		
		if ($parentId == 0) {
			// we create a new array for each top level categories
			$categories[$id] = array('name' => $name, 'children' => array());
			
		} else {
			// the child categories are put int the parent category's array
			$categories[$parentId]['children'][] = array('id' => $id, 'name' => $name);	
		}
	}	
	
	// build combo box options
	$list = '';
	sort($categories);
	foreach ($categories as $key => $value) {
		$name     = $value['name'];
		$children = $value['children'];
		
		$list .= "<optgroup label=\"$name\">"; 
		sort($children);
		foreach ($children as $child) {
			$list .= "<option value=\"{$child['id']}\"";
			if ($child['id'] == $catId) {
				$list.= " selected";
			}
			
			$list .= ">{$child['name']}</option>\r\n";
		}
		
		$list .= "</optgroup>";

	}
	
	return $list;
}