Instruction file imported from dbravoan/dba-stack (.github/instructions/domain-layer.instructions.md). Copyright stays with the author.

Domain Layer Rules

Absolute Constraints

• Zero Illuminate\* or framework imports — this is pure PHP
• Entities MUST extend AggregateRoot from dbravoan/dba-ddd-skeleton
• Every attribute MUST be a Value Object (e.g., UserId, UserEmail, UserName)
• No setters — use semantic domain methods (changeEmail(), activate(), suspend())

Entity Pattern

declare(strict_types=1);

namespace DbaStack\{Context}\{Module}\Domain;

use Dba\DddSkeleton\Domain\Aggregate\AggregateRoot;

final class {Entity} extends AggregateRoot
{
    public function __construct(
        public private(set) {Entity}Id $id,
        public private(set) {Entity}Name $name,
    ) {}

    public static function create({Entity}Id $id, {Entity}Name $name): self
    {
        return new self(id: $id, name: $name);
    }

    public function changeName({Entity}Name $newName): void
    {
        $this->name = $newName;
    }
}

Value Object Pattern

declare(strict_types=1);

namespace DbaStack\{Context}\{Module}\Domain;

final readonly class {Entity}Email
{
    public function __construct(public private(set) string $value)
    {
        if ($value === '' || !filter_var($value, FILTER_VALIDATE_EMAIL)) {
            throw {Entity}InvalidEmail::withValue($value);
        }
    }
}

PHP 8.4 Features to Use

• Asymmetric Visibility: public private(set) on entity properties
• Property Hooks: For computed/derived domain properties
• final readonly: On all Value Objects
• final: On entities and domain services

Repository Contracts

Define interfaces here — implementations go in Infrastructure:

interface {Entity}Repository
{
    public function save({Entity} $entity): void;
    public function search({Entity}Id $id): ?{Entity};
}