ddd.php

<?php
class Domain_Model_User {
  private $id;
  private $name;
}
interface Domain_Model_UserRepository {
  public function save(Domain_Model_User $user);
  public function find($id); // Returns Domain_Model_User
}
class UserService {
  public __construct(Domain_Model_UserRepository $userRepository) { ... }
  public function doSomething();
}
// Some implementations...
class Infrastructure_Persistence_UserRepositoryXml implements Domain_Model_UserRepository {
  ...
}
class Infrastructure_Persistence_UserRepositoryMySql implements Domain_Model_UserRepository {
  ...
}