Getting the world a player is in?

Here is the code I would like to use:

PHP:

$level = $this->getServer()->getLevelByName("Hub");

Now I want to be able to replace "Hub" with the world the player is currently in. How do I do this?

PHP:

$level = $player->getLevel();

PHP:

$level = $player->getLevel()->getName();


In case you want to get the level's name...

Thanks!