Why doesnt this work?

1 
<?php
class card {
    private $cards;
    private $array;

    function setCard($val) {
        $this->cards = array_rand($val, 1);
        return;
    }
    function getCard() {
        return $this->cards;
    }
    function deleteCard($val) {
        $this->array = unset($val[$this->getCard()]);
        return;
    }
}
$randomcard = new card;

$cards = array("Spade" => 1, "Clubs" => 2, "Diamonds" => 3, "Hearts" => 4);

$randomcard->setCard($cards);
$randomcard->deleteCard($cards);
echo $randomcard->getCard();
?>

Also I need to figure out howto actually delete and return from the array I pass in. Any suggestions?