Clear examples of objects requiring an Identity include:
- A person. A person always has an Identity and it's always the same in terms of their name or identification card.
- An order in an e-commerce system. In such a context, every new order created has its own Identity and it's the same over time.
These concepts have an Identity that endures over time. No matter how many times data in the concepts changes, their Identities remain the same. That's what makes them Entities and not Value Objects. In terms of PHP implementation, they would be plain old classes. For example, consider the following in the case of a person:
namespace Ddd\Identity\Domain\Model;
class Person
{
private $identificationNumber;
private $firstName;
private $lastName;
public function __construct(
$anIdentificationNumber, $aFirstName, $aLastName
) {
$this->identificationNumber = $anIdentificationNumber;
$this->firstName = $aFirstName;
$this->lastName...