Symfony2 – Twig – How can I send parameters to the parent template?

Here is a simple example:

base.html.twig:

{# base.html.twig #}
...
<ul>
  <li{% if menu_selected|default('one') == 'one' %} class="selected"{% endif %}>One</li>
  <li{% if menu_selected == 'two' %} class="selected"{% endif %}>Two</li>
  <li{% if menu_selected == 'three' %} class="selected"{% endif %}>Three</li>
</ul>
...

page2.html.twig:

{# page2.html.twig #}
{% extends 'YourBundle::base.html.twig' %}

{% set menu_selected = 'two' %}

Output from rendering page2.html.twig:

<ul>
  <li>One</li>
  <li class="selected">Two</li>
  <li>Three</li>
</ul>