Classe que realiza login para diversos tipos de usuário refatorada.

Login.php

<?php

namespace Login;
use User;

abstract class Login
{
  abstract public function validate(User $user);
}

LoginManager.php

<?php

class LoginManager extends Login
{
  public function  validate(User $user)
  {
    printf("yeah, your user is manager...");
  }
}

LoginSeller.php

<?php

class LoginSeller extends Login
{
  public function  validate(User $user)
  {
    printf("yeah, your user is seller...");
  }
}

test.php

<?php

use User;
use LoginManager;
use LoginSeller;

$loginManager = new LoginManager();
$loginManager->validate(new User('manager'));

$loginSeller = new LoginSeller();
$loginSeller->validate(new User('seller'));