Player in Config

When I add the player to the config, it just replaces it with a new name. How to add multiple names without being replaced?
Sorry my English is not good.
Eg:

Code:

Steve:
   Member: steve1,steve2,....

MyCode:

PHP:

    public function removeplayer($player)
    {
        $form = $this->getserver()->GetPluginManager()->getplugin("FormAPI")->createcustomform(function (player $player, array $data = null){
            if($data === null)
            {
                return True;
            }
            $name = $player->getName();
            $this->Getserver()->dispatchcommand($player, "okp remove " . $data[0]);
            $this->data->setNested("$name.Member", $data[0]);
            $this->data->save();
        });
        $form->settitle("Remove player");
        $form->addinput("Input name .");
        $form->sendtoplayer($player);
        return $form;
    }