how to get the level a player is in and the amount of players

Hello pmmp!
I'm wanting to get the world a player is in and then get the number of players in that world. I have this, but it seems to be the incorrect method :/ could someone help me

PHP:

                   $gamecounter = $player->getLevel->getLevelByName()->getPlayers();
                   $playersArena = count($gamecounter);

 

PHP:

count($player->getLevel()->getPlayers());

 

PHP:

$world = Player->getLevel()->getFolderName(); //string
$worldPlayerCount = count(Player->getLevel()->getPlayers()); //int