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The View

After reading the first part of this tutorial, you have decided that Symfony2 was worth another 10 minutes. Great choice! In this second part, you will learn more about the Symfony2 template engine, Twig. Twig is a flexible, fast, and secure template engine for PHP. It makes your templates more readable and concise; it also makes them more friendly for web designers.

Note

Instead of Twig, you can also use :doc:`PHP </cookbook/templating/PHP>` for your templates. Both template engines are supported by Symfony2 and have the same level of support.

Getting familiar with Twig

Tip

If you want to learn Twig, we highly recommend you to read its official documentation. This section is just a quick overview of the main concepts.

A Twig template is a text file that can generate any text-based format (HTML, XML, CSV, LaTeX, ...). Twig defines two kinds of delimiters:

  • {{ ... }}: Outputs a variable or the result of an expression;
  • {% ... %}: A tag that controls the logic of the template; it is used to execute for loops or if statements for instance.

Below is a minimal template that illustrates a few basics:

<!DOCTYPE html>
<html>
    <head>
        <title>My Webpage</title>
    </head>
    <body>
        <h1>{{ page_title }}</h1>

        <ul id="navigation">
            {% for item in navigation %}
                <li><a href="{{ item.href }}">{{ item.caption }}</a></li>
            {% endfor %}
        </ul>
    </body>
</html>

Tip

Comments can be included inside templates using the {# ... #} delimiter.

To render a template, use the render method from within a controller and pass it any variables needed in the template:

$this->render('AcmeDemoBundle:Demo:hello.html.twig', array(
    'name' => $name,
));

Variables passed to a template can be strings, arrays, or even objects. Twig abstracts the difference between them and let's you access "attributes" of a variable with the dot (.) notation:

{# array('name' => 'Fabien') #}
{{ name }}

{# array('user' => array('name' => 'Fabien')) #}
{{ user.name }}

{# force array lookup #}
{{ user['name'] }}

{# array('user' => new User('Fabien')) #}
{{ user.name }}
{{ user.getName }}

{# force method name lookup #}
{{ user.name() }}
{{ user.getName() }}

{# pass arguments to a method #}
{{ user.date('Y-m-d') }}

Note

It's important to know that the curly braces are not part of the variable but the print statement. If you access variables inside tags don't put the braces around.

Decorating Templates

More often than not, templates in a project share common elements, like the well-known header and footer. In Symfony2, we like to think about this problem differently: a template can be decorated by another one. This works exactly the same as PHP classes: template inheritance allows you to build a base "layout" template that contains all the common elements of your site and defines "blocks" that child templates can override.

The hello.html.twig template inherits from layout.html.twig, thanks to the extends tag:

{# src/Acme/DemoBundle/Resources/views/Demo/hello.html.twig #}
{% extends "AcmeDemoBundle::layout.html.twig" %}

{% block title "Hello " ~ name %}

{% block content %}
    <h1>Hello {{ name }}!</h1>
{% endblock %}

The AcmeDemoBundle::layout.html.twig notation sounds familiar, doesn't it? It is the same notation used to reference a regular template. The :: part simply means that the controller element is empty, so the corresponding file is directly stored under views/.

Now, let's have a look at a simplified layout.html.twig:

{# src/Acme/DemoBundle/Resources/views/layout.html.twig #}
{% extends "::base.html.twig" %}

{% block body %}
    <h1>Demo Bundle</h1>

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

The {% block %} tags define two blocks (body and content) that child templates can fill in. All the block tag does is to tell the template engine that a child template may override those portions of the template. The hello.html.twig template overrides the content block. The other one is defined in a base layout as the layout is itself decorated by another one. When the bundle part of the template name is empty (::base.html.twig), views are looked for in the app/Resources/ directory. This directory stores global templates for your entire project:

{# app/Resources/views/base.html.twig #}
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <title>{% block title %}Welcome!{% endblock %}</title>
        {% block stylesheets %}{% endblock %}
        <link rel="shortcut icon" href="{{ asset('favicon.ico') }}" />
    </head>
    <body>
        {% block body %}{% endblock %}
        {% block javascripts %}{% endblock %}
    </body>
</html>

Using Tags, Filters, and Functions

One of the best feature of Twig is its extensibility via tags, filters, and functions. Symfony2 comes bundled with many of these built-in to ease the work of the template designer.

Including other Templates

The best way to share a snippet of code between several distinct templates is to create a new template that can then be included from other templates.

Create an embedded.html.twig template:

{# src/Acme/DemoBundle/Resources/views/Demo/embedded.html.twig #}
Hello {{ name }}

And change the index.html.twig template to include it:

{# src/Acme/DemoBundle/Resources/views/Demo/hello.html.twig #}
{% extends "AcmeDemoBundle::layout.html.twig" %}

{# override the body block from embedded.html.twig #}
{% block body %}
    {% include "AcmeDemoBundle:Hello:embedded.html.twig" %}
{% endblock %}

Embedding other Controllers

And what if you want to embed the result of another controller in a template? That's very useful when working with Ajax, or when the embedded template needs some variable not available in the main template.

Suppose you've created a fancy action, and you want to include it inside the index template. To do this, use the render tag:

{# src/Acme/DemoBundle/Resources/views/Hello/index.html.twig #}
{% render "AcmeDemoBundle:Demo:fancy" with { 'name': name, 'color': 'green' } %}

Here, the AcmeDemoBundle:Demo:fancy string refers to the fancy action of the Demo controller. The arguments (name and color) act like simulated request variables (as if the fancyAction were handling a whole new request) and are made available to the controller:

// src/Acme/DemoBundle/Controller/DemoController.php

class DemoController extends Controller
{
    public function fancyAction($name, $color)
    {
        // create some object, based on the $color variable
        $object = ...;

        return $this->render('AcmeDemoBundle:Demo:fancy.html.twig', array('name' => $name, 'object' => $object));
    }

    // ...
}

Creating Links between Pages

Speaking of web applications, creating links between pages is a must. Instead of hardcoding URLs in templates, the path function knows how to generate URLs based on the routing configuration. That way, all your URLs can be easily updated by just changing the configuration:

<a href="{{ path('_demo_hello', { 'name': 'Thomas' }) }}">Greet Thomas!</a>

The path function takes the route name and an array of parameters as arguments. The route name is the main key under which routes are referenced and the parameters are the values of the placeholders defined in the route pattern:

// src/Acme/DemoBundle/Controller/DemoController.php
/**
 * @extra:Route("/hello/{name}", name="_demo_hello")
 * @extra:Template()
 */
public function helloAction($name)
{
    return array('name' => $name);
}

Tip

The url function generates absolute URLs: {{ url('_demo_hello', { 'name': 'Thomas' }) }}.

Including Assets: images, JavaScripts, and stylesheets

What would the Internet be without images, JavaScripts, and stylesheets? Symfony2 provides the asset function to deal with them easily:

<link href="{{ asset('css/blog.css') }}" rel="stylesheet" type="text/css" />

<img src="{{ asset('images/logo.png') }}" />

The asset function's main purpose is to make your application more portable. Thanks to this function, you can move the application root directory anywhere under your web root directory without changing anything in your template's code.

Escaping Variables

Twig is configured to automatically escapes all output by default. Read Twig documentation to learn more about output escaping and the Escaper extension.

Final Thoughts

Twig is simple yet powerful. Thanks to layouts, blocks, templates and action inclusions, it is very easy to organize your templates in a logical and extensible way.

You have only been working with Symfony2 for about 20 minutes, but you can already do pretty amazing stuff with it. That's the power of Symfony2. Learning the basics is easy, and you will soon learn that this simplicity is hidden under a very flexible architecture.

But I'm getting ahead of myself. First, you need to learn more about the controller and that's exactly the topic of the next part of this tutorial. Ready for another 10 minutes with Symfony2?