PHP中封装性的案例研究

class Cart {
    private $items = [];

    // 添加商品到购物车
    public function addItem($productId, $quantity) {
        // 检查商品是否已经存在于购物车中
        if (isset($this->items[$productId])) {
            $this->items[$productId] += $quantity;
        } else {
            $this->items[$productId] = $quantity;
        }
    }

    // 从购物车中移除商品
    public function removeItem($productId, $quantity) {
        // 检查商品是否存在于购物车中
        if (isset($this->items[$productId])) {
            $this->items[$productId] -= $quantity;
            if ($this->items[$productId] <= 0) {
                unset($this->items[$productId]);
            }
        }
    }

    // 获取购物车中的所有商品
    public function getItems() {
        return $this->items;
    }

    // 获取购物车中商品的总数量
    public function getTotalQuantity() {
        $total = 0;
        foreach ($this->items as $quantity) {
            $total += $quantity;
        }
        return $total;
    }

    // 获取购物车中商品的总金额
    public function getTotalAmount($prices) {
        $total = 0;
        foreach ($this->items as $productId => $quantity) {
            if (isset($prices[$productId])) {
                $total += $prices[$productId] * $quantity;
            }
        }
        return $total;
    }
}

// 创建一个购物车对象
$cart = new Cart();

// 添加商品到购物车
$cart->addItem('1', 2);
$cart->addItem('2', 1);

// 获取购物车中的所有商品
$items = $cart->getItems();

// 输出购物车中的商品信息
foreach ($items as $productId => $quantity) {
    echo "商品ID：{$productId}，数量：{$quantity}" . PHP_EOL;
}

// 输出购物车中商品的总数量和总金额
$prices = [
    '1' => 10.99,
    '2' => 5.99
];
$totalQuantity = $cart->getTotalQuantity();
$totalAmount = $cart->getTotalAmount($prices);
echo "总数量：{$totalQuantity}，总金额：{$totalAmount}" . PHP_EOL;

// 从购物车中移除商品
$cart->removeItem('1', 1);
$cart->removeItem('2', 1);