How to Override Templates from Third-Party Bundles

The Symfony community prides itself on creating and maintaining high quality bundles (see KnpBundles.com) for a large number of different features. Once you use a third-party bundle, you'll likely need to override and customize one or more of its templates.

Suppose you've installed an imaginary open-source AcmeBlogBundle in your project. And while you're really happy with everything, you want to override the template for a blog list page. Inside the bundle, the template you want to override lives at Resources/views/Blog/index.html.twig.

To override the bundle template, just copy the index.html.twig template from the bundle to app/Resources/AcmeBlogBundle/views/Blog/index.html.twig (the app/Resources/AcmeBlogBundle directory won't exist, so you'll need to create it). You're now free to customize the template.

Instead of overriding an entire template, you may just want to override one or more blocks. However, since you are overriding the template you want to extend from, you would end up in an infinite loop error. The solution is to use the special ! prefix in the template name to tell Symfony that you want to extend from the original template, not from the overridden one:

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{# app/Resources/AcmeBlogBundle/views/Blog/index.html.twig #}
{# the special '!' prefix avoids errors when extending from an overridden template #}
{% extends "@!AcmeBlog/index.html.twig" %}

{% block some_block %}
    ...
{% endblock %}

This logic also applies to any template that lives in a bundle: just follow the convention: app/Resources/{BUNDLE_NAME}/views/{PATH/TO/TEMPLATE.html.twig}.