get render html in variable in symfony4 code example

Example: controller to render static data symfony

{# templates/base.html.twig #}

{# ... #}
<div id="sidebar">
    {# if the controller is associated with a route, use the path() or url() functions #}
    {{ render(path('latest_articles', {max: 3})) }}
    {{ render(url('latest_articles', {max: 3})) }}

    {# if you don't want to expose the controller with a public URL,
       use the controller() function to define the controller to execute #}
    {{ render(controller(
        'App\\Controller\\BlogController::recentArticles', {max: 3}
    )) }}
</div>