Modules and layers

src/Billing/
├── Domain/
│   ├── Entities/          # OrderEntity, PlanEntity, SubscriptionEntity…
│   ├── ValueObjects/      # Price, BillingCycle, ExternalId…
│   ├── Repositories/      # OrderRepositoryInterface…
│   ├── Events/            # OrderCreatedEvent, SubscriptionCreatedEvent…
│   ├── Exceptions/        # AlreadyPaidException…
│   └── Services/          # BillingService, OrderFulfillmentService
├── Application/
│   ├── Commands/          # CreateOrderCommand, PayOrderCommand…
│   ├── CommandHandlers/   # one per command
│   └── Listeners/
└── Infrastructure/
    ├── BillingModuleBootstrapper.php
    ├── Repositories/DoctrineOrm/
    ├── Payments/          # gateway contracts and built-in gateways
    ├── Tax/
    └── Currency/

#[ORM\Entity]
#[ORM\Table(name: 'category')]
class CategoryEntity
{
    #[ORM\Embedded(class: Id::class, columnPrefix: false)]
    private Id $id;

    #[ORM\Embedded(class: Title::class, columnPrefix: false)]
    private Title $title;

    public function __construct(Title $title)
    {
        $this->id = new Id();
        $this->title = $title;
        $this->createdAt = new DateTimeImmutable();
    }
}

$title = new Title('Marketing');   // throws InvalidValueException when empty

#[Handler(CreateCategoryCommandHandler::class)]
class CreateCategoryCommand
{
    public Title $title;

    public function __construct(string $title)
    {
        $this->title = new Title($title);
    }
}

class CreateCategoryCommandHandler
{
    public function __construct(
        private CategoryRepositoryInterface $repo,
        private EventDispatcherInterface $dispatcher,
    ) {}

    public function handle(CreateCategoryCommand $cmd): CategoryEntity
    {
        $category = new CategoryEntity(title: $cmd->title);

        $this->repo->add($category);
        $this->dispatcher->dispatch(new CategoryCreatedEvent($category));

        return $category;
    }
}

$plans = $repo
    ->filterByStatus($status)
    ->orderBy('price', 'ASC')
    ->slice(0, 20);