zen_get_category_description($category_id, $fn_language_id)
该函数主要通过指定的目录ID和指定的语言ID返回一个目录的描述。跟zen_get_category_name函数差不多一样，只是返回的结果不一样
主要查询了 categories_description 表。在includes/database_tables.php中定义：
define(‘TABLE_CATEGORIES_DESCRIPTION’, DB_PREFIX . ‘categories_description’);
*/function zen_get_category_description($category_id, $fn_language_id) {
global $db;
$category_query = "select categories_description
from " . TABLE_CATEGORIES_DESCRIPTION . "
where categories_id = '" . $category_id . "'
and language_id = '" . $fn_language_id . "'";
$category = $db->Execute($category_query);
return $category->fields['categories_description'];
}