DTO (Data Transfer Object)

Why it is needed

• Isolates the internal model from the external API — a DB schema change will not break the API response
• Explicitly documents what data is passed between layers
• Convenient for validating input data (Request DTO) and shaping responses (Response DTO)

Example

class CreateUserDTO {
  public function __construct(
    public readonly string $name,
    public readonly string $email,
    public readonly string $password,
  ) {}
}

DTO vs Entity vs ViewModel

• Entity — a domain model object with identity (exists in the DB)
• DTO — a transport container with no identity
• ViewModel — a DTO specifically shaped for display in a UI/template