Dto

Name: DTO (Data Transfer Object) Description: Readonly data containers with a fromArray factory method used to pass structured data between application layers — especially for external API responses and service boundaries. Compatible Agents: general-purpose, backend Tags: DataObjects/**/*.php, laravel, php, backend, dto, data-object, readonly

Rules

• Use readonly class with constructor promotion
• Include a static fromArray(array $data): static factory method
• Place DTOs in the relevant service's DataObjects/ directory
• DTOs are immutable — never add setters or mutable state
• Handle API field name variations (PascalCase, camelCase, snake_case) in fromArray()
• Use nullable types for optional fields
• Keep DTOs free of business logic — they are data containers only
• All properties must have explicit types — no untyped properties

Examples

readonly class CustomerData
{
    public function __construct(
        public string $id,
        public ?string $name,
        public ?string $email,
    ) {}

    public static function fromArray(array $data): static
    {
        return new static(
            id: (string) ($data['ID'] ?? $data['id'] ?? ''),
            name: $data['Name'] ?? $data['name'] ?? null,
            email: $data['Email'] ?? $data['email'] ?? null,
        );
    }
}

// Usage
$customer = CustomerData::fromArray($apiResponse);
echo $customer->name;

Anti-Patterns

• Adding setters or mutable state to a DTO
• Including business logic inside a DTO
• Using a DTO as a model replacement (DTOs don't persist to the database)
• Not handling API field name variations (assuming a single naming convention)
• Leaving properties untyped or using mixed without narrowing
• Placing DTOs in a global DataObjects/ folder instead of within the relevant service directory

References

• PHP Readonly Classes
• Related: Services/SKILL.md — DTOs are typically returned by service classes
• Related: Saloon/SKILL.md — Saloon integrations return typed DTOs