twig_extension.rst

.. index::
   single: Twig extensions

How to write a custom Twig Extension

The main motivation for writing an extension is to move often used code into a reusable class like adding support for internationalization. An extension can define tags, filters, tests, operators, global variables, functions, and node visitors.

Creating an extension also makes for a better separation of code that is executed at compilation time and code needed at runtime. As such, it makes your code faster.

Tip

Before writing your own extensions, have a look at the Twig official extension repository.

Create the Extension Class

Note

This cookbook describes how to write a custom Twig extension as of Twig 1.12. If you are using an older version, please read Twig extensions documentation legacy.

To get your custom functionality you must first create a Twig Extension class. As an example you'll create a price filter to format a given number into price:

// src/Acme/DemoBundle/Twig/AcmeExtension.php
namespace Acme\DemoBundle\Twig;

class AcmeExtension extends \Twig_Extension
{
    public function getFilters()
    {
        return array(
            new \Twig_SimpleFilter('price', array($this, 'priceFilter')),
        );
    }

    public function priceFilter($number, $decimals = 0, $decPoint = '.', $thousandsSep = ',')
    {
        $price = number_format($number, $decimals, $decPoint, $thousandsSep);
        $price = '$'.$price;

        return $price;
    }

    public function getName()
    {
        return 'acme_extension';
    }
}

Tip

Along with custom filters, you can also add custom functions and register global variables.

Register an Extension as a Service

Now you must let the Service Container know about your newly created Twig Extension:

.. configuration-block::

    .. code-block:: yaml

        # src/Acme/DemoBundle/Resources/config/services.yml
        services:
            acme.twig.acme_extension:
                class: Acme\DemoBundle\Twig\AcmeExtension
                tags:
                    - { name: twig.extension }

    .. code-block:: xml

        <!-- src/Acme/DemoBundle/Resources/config/services.xml -->
        <services>
            <service id="acme.twig.acme_extension" class="Acme\DemoBundle\Twig\AcmeExtension">
                <tag name="twig.extension" />
            </service>
        </services>

    .. code-block:: php

        // src/Acme/DemoBundle/Resources/config/services.php
        use Symfony\Component\DependencyInjection\Definition;

        $container
            ->register('acme.twig.acme_extension', '\Acme\DemoBundle\Twig\AcmeExtension')
            ->addTag('twig.extension');

Note

Keep in mind that Twig Extensions are not lazily loaded. This means that there's a higher chance that you'll get a CircularReferenceException or a ScopeWideningInjectionException if any services (or your Twig Extension in this case) are dependent on the request service. For more information take a look at :doc:`/cookbook/service_container/scopes`.

Using the custom Extension

Using your newly created Twig Extension is no different than any other:

{# outputs $5,500.00 #}
{{ '5500'|price }}

Passing other arguments to your filter:

{# outputs $5500,2516 #}
{{ '5500.25155'|price(4, ',', '') }}

Learning further

For a more in-depth look into Twig Extensions, please take a look at the Twig extensions documentation.