use

Template inheritance is one of the most powerful features of Twig but it is limited to single inheritance; a template can only extend one other template. This limitation makes template inheritance simple to understand and easy to debug:

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{% extends "base.html.twig" %}

{% block title %}{% endblock %}
{% block content %}{% endblock %}

Horizontal reuse is a way to achieve the same goal as multiple inheritance, but without the associated complexity:

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{% extends "base.html.twig" %}

{% use "blocks.html.twig" %}

{% block title %}{% endblock %}
{% block content %}{% endblock %}

The use statement tells Twig to import the blocks defined in blocks.html.twig into the current template (it's like macros, but for blocks):

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{# blocks.html.twig #}
{% block sidebar %}{% endblock %}

In this example, the use statement imports the sidebar block into the main template. The code is mostly equivalent to the following one (the imported blocks are not outputted automatically):

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{% extends "base.html.twig" %}

{% block sidebar %}{% endblock %}
{% block title %}{% endblock %}
{% block content %}{% endblock %}

The main template can also override any imported block. If the template already defines the sidebar block, then the one defined in blocks.html.twig is ignored. To avoid name conflicts, you can rename imported blocks:

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{% extends "base.html.twig" %}

{% use "blocks.html.twig" with sidebar as base_sidebar, title as base_title %}

{% block sidebar %}{% endblock %}
{% block title %}{% endblock %}
{% block content %}{% endblock %}

The parent() function automatically determines the correct inheritance tree, so it can be used when overriding a block defined in an imported template:

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{% extends "base.html.twig" %}

{% use "blocks.html.twig" %}

{% block sidebar %}
    {{ parent() }}
{% endblock %}

{% block title %}{% endblock %}
{% block content %}{% endblock %}

In this example, parent() will correctly call the sidebar block from the blocks.html.twig template.

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{% extends "base.html.twig" %}

{% use "blocks.html.twig" with sidebar as parent_sidebar %}

{% block sidebar %}
    {{ block('parent_sidebar') }}
{% endblock %}