PHP8.3新特性实战：类型安全增强与属性钩子深度解析

一、类型系统增强

PHP8.3引入的精细化类型控制：

// 新引入的精确类型检查
class Account {
    public readonly string $accountId;
    
    public function __construct(
        public string $username,
        public DateTimeImmutable $createdAt = new DateTimeImmutable(),
        string|Stringable $accountId = null
    ) {
        // 类型细化检查
        $this->accountId = $accountId ?? $this->generateUuid();
        
        // 运行时类型验证
        if (!is_string($this->accountId) {
            throw new TypeError("Account ID must be string");
        }
    }
    
    // 带类型检查的属性钩子
    public function __get(string $name): mixed {
        if ($name === 'balance') {
            return $this->fetchBalance();
        }
        throw new Error("Undefined property: $name");
    }
    
    private function generateUuid(): string {
        return bin2hex(random_bytes(16));
    }
}

// 使用示例
$account = new Account("phpuser");
echo $account->accountId; // 自动生成UUID
echo $account->balance; // 触发__get钩子

核心优势：编译时类型检查、运行时验证、代码安全性、IDE友好

二、属性钩子实战

1. 智能属性访问控制

class SmartDTO {
    private array $data = [];
    private array $dirty = [];
    
    public function __set(string $name, mixed $value): void {
        if (!property_exists($this, $name)) {
            throw new InvalidArgumentException("Invalid property: $name");
        }
        
        $this->dirty[$name] = true;
        $this->data[$name] = $value;
    }
    
    public function __get(string $name): mixed {
        $this->validateProperty($name);
        return $this->data[$name] ?? null;
    }
    
    public function isDirty(): bool {
        return !empty($this->dirty);
    }
    
    private function validateProperty(string $name): void {
        if (!array_key_exists($name, $this->data)) {
            throw new RuntimeException("Property $name not initialized");
        }
    }
}

// 使用示例
$dto = new SmartDTO();
$dto->name = "PHP8.3"; // 触发__set
echo $dto->name; // 触发__get

2. 类型转换钩子

class TypedArray {
    private array $items = [];
    
    public function __construct(
        private string $itemType
    ) {}
    
    public function add(mixed $item): void {
        $this->validateType($item);
        $this->items[] = $item;
    }
    
    public function __serialize(): array {
        return [
            'type' => $this->itemType,
            'items' => $this->items
        ];
    }
    
    public function __unserialize(array $data): void {
        if ($data['type'] !== $this->itemType) {
            throw new RuntimeException("Type mismatch");
        }
        $this->items = $data['items'];
    }
    
    private function validateType(mixed $item): void {
        $expected = $this->itemType;
        if (!$item instanceof $expected) {
            throw new TypeError("Item must be of type $expected");
        }
    }
}

// 使用示例
$list = new TypedArray(DateTimeInterface::class);
$list->add(new DateTime()); // 合法
$list->add("2023-01-01"); // 抛出TypeError

三、电商系统实战案例

1. 类型安全的订单系统

class Order {
    public readonly string $orderId;
    private array $items = [];
    private DateTimeImmutable $createdAt;
    
    public function __construct(
        public readonly Customer $customer,
        ?string $orderId = null
    ) {
        $this->orderId = $orderId ?? $this->generateOrderId();
        $this->createdAt = new DateTimeImmutable();
    }
    
    public function addItem(OrderItem $item): void {
        $this->items[] = $item;
    }
    
    public function calculateTotal(): Money {
        return array_reduce(
            $this->items,
            fn(Money $total, OrderItem $item) => $total->add($item->getPrice()),
            new Money(0, $this->customer->getCurrency())
        );
    }
    
    public function __serialize(): array {
        return [
            'orderId' => $this->orderId,
            'customer' => $this->customer,
            'items' => $this->items,
            'createdAt' => $this->createdAt->format(DateTimeInterface::ATOM)
        ];
    }
    
    private function generateOrderId(): string {
        return 'order_'.bin2hex(random_bytes(8));
    }
}

// 使用示例
$customer = new Customer('test@example.com');
$order = new Order($customer);
$order->addItem(new OrderItem('PHP8.3 Book', new Money(2999, 'USD')));
$total = $order->calculateTotal();