Email.php

<?php
/**
 * Created by PhpStorm.
 * User: chentao
 * Date: 2019/3/22
 * Time: 3:33 PM
 */

namespace Helper;


final class Email
{

    private $email;

    private function __construct($email)
    {
        $this->ensureIsValidEmail($email);

        $this->email = $email;
    }

    public static function fromString($email)
    {
        return new self($email);
    }

    public function __toString()
    {
        return $this->email;
    }

    private function ensureIsValidEmail($email)
    {
        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            throw new \InvalidArgumentException(
                sprintf('"%s" is not a valid email address', $email)
            );
        }
    }
}