How to get Players in Multiple worlds

How do i get how many players there are in Multiple worlds and add them so when i add it to a form it will show the player count of 2 worlds

 

$this->getServer()->getOnlinePlayers()

 

yes but in worlds

 

level->getPlayers();

 

PHP:

$playerCount = 0;
$worlds = ["world1", "world2"]; // Add which worlds will calculate
foreach($worlds as $world){
  if(!Server::getInstance()->isLevelLoaded($world)){
    Server::getInstance()->loadLevel($world);
  }
  $level = Server::getInstance()->getLevelByName($world);
  $playerCount += count($level->getPlayers());
}

// Do what do you want with $playerCount