DDD user demo

<?php

class User {

    /** @var string */
    protected $password;

    /**
     * @return string
     */
    public function getPassword()
    {
        return $this->password;
    }

    /**
     * @param string $password
     */
    public function __construct(string $password)
    {
        $this->password = $password;
    }

    /**
     * @param string $password
     *
     * @return User
     */
    public static function create(string $password)
    {
        return new self($password);
    }

    /**
     * @param User   $user
     * @param string $password
     */
    public function changePassword(User &$user, string $password)
    {
        $user = self::create($password);
    }
}

$user = User::create("pass1");
print_r($user->getPassword());

$user->changePassword($user, 'pass2');
print_r($user->getPassword());