How to hide nametag on item

$player = $ev->getEntity();
$Nid = $ev->getNewItem()->getID();
$Oid = $ev->getOldItem()->getID();

public function onArmorChange(EntityArmorChangeEvent $ev){
if($player instanceof Player){
if($Nid === 397){
$sender->getPlayer->setNameTagVisible(false);

}elseif($Oid === 397){
$sender->getPlayer->setNameTagVisible(true);
}
}
}
}​

 

Are you asking or are you giving instructions?

 

I giving instruction

 

Not working, undefined methods etc.