public function create_category($parent_category = null)
 {
     if ($this->post) {
         $name = $this->PostData("category_name");
         $parent_category = $this->PostData("parent_category");
         if ($parent_category) {
             $name = $parent_category . "/" . $name;
         }
         if (File::create_category($name)) {
             Site::flash("notice", "Category created successfully");
             Redirect("admin/files");
         } else {
             Site::flash("error", "Unable to create category");
             Redirect("admin/files");
         }
     }
     if (!$parent_category) {
         if (isset($_GET['parent_category'])) {
             $parent_category = $_GET['parent_category'];
         }
     }
     $this->assign("parent_category", $parent_category);
     $this->title = "Create File Category";
     $this->render("file/create_category.tpl");
 }