public function admin_init()
 {
     $createswpmuser = filter_input(INPUT_POST, 'createswpmuser');
     if (!empty($createswpmuser)) {
         SwpmAdminRegistration::get_instance()->register();
     }
     $editswpmuser = filter_input(INPUT_POST, 'editswpmuser');
     if (!empty($editswpmuser)) {
         $id = filter_input(INPUT_GET, 'member_id', FILTER_VALIDATE_INT);
         SwpmAdminRegistration::get_instance()->edit($id);
     }
     $createswpmlevel = filter_input(INPUT_POST, 'createswpmlevel');
     if (!empty($createswpmlevel)) {
         SwpmMembershipLevel::get_instance()->create();
     }
     $editswpmlevel = filter_input(INPUT_POST, 'editswpmlevel');
     if (!empty($editswpmlevel)) {
         $id = filter_input(INPUT_GET, 'id');
         SwpmMembershipLevel::get_instance()->edit($id);
     }
     $update_category_list = filter_input(INPUT_POST, 'update_category_list');
     if (!empty($update_category_list)) {
         include_once 'class.swpm-category-list.php';
         SwpmCategoryList::update_category_list();
     }
 }
 public static function get_instance()
 {
     self::$_instance = empty(self::$_instance) ? new SwpmMembershipLevel() : self::$_instance;
     return self::$_instance;
 }