Zend 2 crazy flash notices with namespaces

gistfile1.php

<?php
// Set message
    $this->flashMessenger()
      ->setNamespace("success")
      ->addMessage("You've been logged out");
    return $this->redirect()->toUrl('/');

// Retrieve message
    $notice = null;
    $flash = $this->flashMessenger();

    $flash->setNamespace('success');
    if ($flash->hasMessages())
      $notice = array('type' => 'success', 'message' => $flash->getMessages()[0]);

    $flash->setNamespace('error');
    if ($flash->hasMessages())
      $notice = array('type' => 'error', 'message' => $flash->getMessages()[0]);

    $this->layout()->notice = $notice;