gistfile1.txt

class UserMailer {
  private $user;
  
  public function __construct($user)  
  {  
    $this->user = $user;  
  }
  
  public function activation_deliver()
  {
    echo $this->user->email;
  }
}

class User {
  public $email = "luis@zamith.pt";
}

$user = new User;
$mailer = new UserMailer($user);

$mailer->activation_deliver();