ObjectCalisthenics-Rule3-After.php

<?php
class Email {
    public $email;

    public function __construct($email)
    {
        if (filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
            throw new InvalidEmailException;
        }

        return $this->email = $email;
    }
}

class Order
{
    public function notifyBuyer($email)
    {
        return $this->repository->sendEmail(new Email($email));
    }
}