Manually remember me for Symfony2

UserProvider.php

class UserProvider
{
    /** ... */

    protected function enableRememberMe($username)
    {
        $rememberMeValue = $this->generateRememberMeCookie($username);
        $this->session->set('REMEMBER_ME', $rememberMeValue);
    }

    protected function generateRememberMeCookie($username)
    {
        $key = 'ThisTokenIsNotSoSecretChangeIt';
        $class = 'MyCompany\Bundle\UserBundle\Entity\User';
        $password = 'none';
        $expires = time()+2592000;

        $hash = hash('sha256', $class.$username.$expires.$password.$key);

        return $this->encodeCookie(
            array(
                $class,
                base64_encode($username),
                $expires,
                $hash
            )
        );
    }

    /**
     * Encodes the cookie parts
     *
     * @param array $cookieParts
     *
     * @return string
     */
    protected function encodeCookie(array $cookieParts)
    {
        return base64_encode(implode(':', $cookieParts));
    }
}