templates.rst

Templates

When PHP was created 20 years ago, developers loved its simplicity and how well it blended HTML and dynamic code. But as time passed, other template languages - like Twig - were created to make templating even better.

.. best-practice::

    Use Twig templating format for your templates.

Generally speaking, PHP templates are much more verbose than Twig templates because they lack native support for lots of modern features needed by templates, like inheritance, automatic escaping and named arguments for filters and functions.

Twig is the default templating format in Symfony and has the largest community support of all non-PHP template engines (it's used in high profile projects such as Drupal 8).

In addition, Twig is the only template format with guaranteed support in Symfony 3.0. As a matter of fact, PHP may be removed from the officially supported template engines.

Template Locations

.. best-practice::

    Store all your application's templates in ``app/Resources/views/`` directory.

Traditionally, Symfony developers stored the application templates in the Resources/views/ directory of each bundle. Then they used the Twig namespaced path to refer to them (e.g. @AcmeDemo/Default/index.html.twig).

But for the templates used in your application, it's much more convenient to store them in the app/Resources/views/ directory. For starters, this drastically simplifies their logical names:

Templates Stored inside Bundles	Templates Stored in app/
@AcmeDemo/index.html.twig	index.html.twig
@AcmeDemo/Default/index.html.twig	default/index.html.twig
@AcmeDemo/Default/subdir/index.html.twig	default/subdir/index.html.twig

Another advantage is that centralizing your templates simplifies the work of your designers. They don't need to look for templates in lots of directories scattered through lots of bundles.

.. best-practice::

    Use lowercased snake_case for directory and template names.

Twig Extensions

.. best-practice::

    Define your Twig extensions in the ``AppBundle/Twig/`` directory. Your
    application will automatically detect them and configure them.

Our application needs a custom md2html Twig filter so that we can transform the Markdown contents of each post into HTML.

To do this, first, install the excellent Parsedown Markdown parser as a new dependency of the project:

$ composer require erusev/parsedown

Then, create a new Markdown class that will be used later by the Twig extension. It just needs to define one single method to transform Markdown content into HTML:

namespace AppBundle\Utils;

class Markdown
{
    private $parser;

    public function __construct()
    {
        $this->parser = new \Parsedown();
    }

    public function toHtml($text)
    {
        $html = $this->parser->text($text);

        return $html;
    }
}

Next, create a new Twig extension and define a new filter called md2html using the Twig_SimpleFilter class. Inject the newly defined Markdown class in the constructor of the Twig extension:

namespace AppBundle\Twig;

use AppBundle\Utils\Markdown;

class AppExtension extends \Twig_Extension
{
    private $parser;

    public function __construct(Markdown $parser)
    {
        $this->parser = $parser;
    }

    public function getFilters()
    {
        return array(
            new \Twig_SimpleFilter(
                'md2html',
                array($this, 'markdownToHtml'),
                array('is_safe' => array('html'), 'pre_escape' => 'html')
            ),
        );
    }

    public function markdownToHtml($content)
    {
        return $this->parser->toHtml($content);
    }

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

And that's it!

If you're using the :ref:`default services.yml configuration <service-container-services-load-example>`, you're done! Symfony will automatically know about your new service and tag it to be used as a Twig extension.