A simple script to test my understanding of value objects.

value_object.php

<?php

abstract class EmailValidator
{
  function __construct($value)
  {
    if(!$this->validate($value)) {
      throw new InvalidArgumentException;
    }

    $this->email = $value;
  }


  private function validate($value)
  {
    if(!filter_var($value, FILTER_VALIDATE_EMAIL)) {
      return false;
    }

    return true;
  }
}


class Email
extends EmailValidator
{
  public function get()
  {
    return $this->email;
  }
}

// Tests

var_dump(
  new Email('hellopayton@gmail.com'), // object
  new Email('test'),                  // throws InvalidArgumentException
  new Email(null)                     // throws InvalidArgumentException
);