function getPrice() { return $this->price * $this->qty; } function getVAT() { return $this->price * $this->VAT * $this->qty; } function totalPrice() { return $this->price * $this->qty; } function setQty($qty) { if ($qty < 13) { $this->qty = $qty; } else { echo "Must be 12 or less"; } } } $c = new Computer("xxxxx", "comp1", 100); $c->setQty(10); echo $c . PHP_EOL; echo $c->getVAT() . PHP_EOL; echo $c->totalPrice() . PHP_EOL; $d = new Contract("cccc", "Internet", 33.95); $d->setQty(10); echo $d . PHP_EOL; echo $d->getPrice(); echo $d->totalPrice();