PHP 属性与反射元编程：Attribute 语法、ReflectionAttribute 与属性驱动设计

$rc  = new ReflectionClass(UserController::class);
$rm  = $rc->getMethod('index');
$rp  = $rc->getProperty('name');

// 全部属性
$attrs = $rm->getAttributes();

// 按类名过滤
$routes = $rm->getAttributes(Route::class);

// 按父类/接口过滤（子类也能命中）
$handlers = $rm->getAttributes(HandlerInterface::class, ReflectionAttribute::IS_INSTANCEOF);

foreach ($rm->getAttributes(Route::class) as $attr) {
    $route = $attr->newInstance();       // 实例化属性类
    echo $route->path, PHP_EOL;

    // 不想实例化时，可先看原始参数
    var_dump($attr->getArguments());     // ['/api/users', 'GET']
}

class Child extends Base
{
    #[Override]
    public function save(): void {}      // OK
    #[Override]
    public function seve(): void {}      // 编译期报错：父类没有 seve
}

function login(string $user, #[SensitiveParameter] string $password) {}
// 抛异常时堆栈里 password 显示为 Object，不再明文泄漏

#[Attribute(Attribute::TARGET_METHOD | Attribute::IS_REPEATABLE)]
final class Get
{
    public function __construct(
        public readonly string $path,
        public readonly array $middleware = [],
    ) {}
}

final class UserController
{
    #[Get('/api/users')]
    public function index(Request $r): Response { /* ... */ }

    #[Get('/api/users/{id}', middleware: ['auth'])]
    public function show(int $id): Response { /* ... */ }
}

final class Router
{
    private array $routes = [];

    public function register(string $class): void
    {
        foreach ((new ReflectionClass($class))->getMethods() as $rm) {
            foreach ($rm->getAttributes(Get::class) as $attr) {
                $g = $attr->newInstance();
                $this->routes['GET'][$g->path] = [
                    'handler'    => [$class, $rm->getName()],
                    'middleware' => $g->middleware,
                ];
            }
        }
    }
}

// 调用时按反射参数名，把 path 变量注入到方法参数
$args = [];
foreach ((new ReflectionMethod($class, $method))->getParameters() as $p) {
    $args[] = $params[$p->getName()] ?? null;
}
call_user_func([$instance, $method], ...$args);

use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity(repositoryClass: UserRepository::class)]
#[ORM\Table(name: 'users')]
class User
{
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column(type: 'integer')]
    private int $id;

    #[ORM\Column(type: 'string', length: 180, unique: true)]
    private string $email;

    #[ORM\ManyToOne(targetEntity: Team::class, inversedBy: 'users')]
    #[ORM\JoinColumn(nullable: false)]
    private Team $team;
}

#[Attribute(Attribute::TARGET_PROPERTY | Attribute::TARGET_PARAMETER)]
final class Length
{
    public function __construct(
        public readonly int $min,
        public readonly int $max,
        public readonly string $message = '长度不合法',
    ) {}
}
// Email 属性同理，只带一个 message 参数

final class RegisterRequest
{
    public function __construct(
        #[Length(min: 3, max: 20)] public readonly string $username,
        #[Email]                   public readonly string $email,
    ) {}
}

final class Validator
{
    public function validate(object $dto): array
    {
        $errors = [];
        foreach ((new ReflectionClass($dto))->getProperties() as $rp) {
            $value = $rp->getValue($dto);
            foreach ($rp->getAttributes() as $attr) {
                $rule = $attr->newInstance();
                if ($rule instanceof Length && mb_strlen($value) < $rule->min) {
                    $errors[$rp->getName()] = $rule->message;
                }
            }
        }
        return $errors;
    }
}

// 旧：注解
/** @ORM\Column(type="string", length=180) */
private string $email;

// 新：属性
#[ORM\Column(type: 'string', length: 180)]
private string $email;

$meta = $cache->rememberForever('routes_meta', fn () => (new Router())->compile($controllers));

final class Container
{
    private array $routes = [];

    public function scan(string ...$classes): void
    {
        foreach ($classes as $class) {
            foreach ((new ReflectionClass($class))->getMethods() as $rm) {
                foreach ($rm->getAttributes(Route::class) as $attr) {
                    $r = $attr->newInstance();
                    $this->routes[$r->method][$r->path] = [$class, $rm->getName()];
                }
            }
        }
    }

    public function dispatch(string $method, string $path): string
    {
        [$class, $action] = $this->routes[$method][$path] ?? [null, null];
        return $class ? (new $class())->{$action}() : '404 Not Found';
    }
}