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06.

Twig

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Now for the absolutely hardest part of Symfony. I'm kidding! We're talking about templates: those files where we mix HTML tags and dynamic data to build our page. We already saw that these are rendered using the templating service, usually from inside a controller.

We also know that they're written in Twig, a language that feels a lot like PHP, but was made specifically to be awesome at doing templating tasks, like looping, rendering other templates, and handling layouts.

If you haven't seen Twig before, trust me, you're going to love it! It's easy and a joy to work with.

Tip

If you do end up hating Twig, you can use normal PHP templates as well, though 3rd party bundles don't support these as well.

The Print Syntax

Twig only has two different tags and we've already seen the first one: the print tag:

{{ name }}

No matter what, if you want to print something in Twig, then you'll use this double curly brace format. I call this the "say something" tag, and it's basically the same as opening PHP and using echo:

<?php echo $name ?>

In our template, we're printing the name variable, which was passed to the template from the controller.

The Do Something Sytnax

The second tag is the "do something" tag. Its syntax is {% %} and we use it to do things like looping, defining variables, and if statements. It's easier to see, so let's pass the count variable into our template:

// src/Yoda/EventBundle/Controller/DefaultController.php
// ...

public function indexAction($count, $firstName)
{
    return $this->render(
        'EventBundle:Default:index.html.twig',
        array('name' => $firstName, 'count' => $count)
    );
}

Now, use Twig's for tag to print the name a certain number of times:

{# src/Yoda/EventBundle/Resources/views/Default/index.html.twig #}

{% for i in 1..count %}
    Hello <strong>{{ name }}</strong> # {{ i }}!<br/>
{% endfor %}

Now refresh! There are a finite number of "do something" tags and there's even a handy list on Twig's Documentation page. Scroll down a little bit and check out the list on the left.

Tip

Symfony adds just a few more Twig "do something" tags. Find them in the Symfony Reference documentation.

So the {{ }} syntax prints things and the {% %} performs other language actions. If you've got this down, I'd say you've just about mastered Twig.

Comments

Ok, I hate to lie to you, so there is a third tag, but it's just used to write comments.

{# Hello comments! #}

Filters

But wait, there's more! Twig has a lot of nice tricks and sugar, like filters! We can use the upper filter to capitalize the name variable:

Hello <strong>{{ name|upper }}</strong> # {{ i }}!<br/>

If you're used to piping things together in a UNIX terminal, this works the same way. Back on the Documentation page, you'll find a big list of filters, You can even use filters on top of filters.

Twig also has functions and a cool thing called tests, which lets you write things like {% if i is odd %}. But that's all just extra fun stuff.

Tip

If you want to get deeper with these types of tricks or want to help your frontend designer get started, check out our Twig Screencast.

Extending a Base Layout

Despite all my Twig hype, our template is depressing: it's got some HTML, but no layout. If only we had a base layout template that could decorate all of our page.

Oh right, there is one, and it lives in the app/Resources/views directory. Actually, it's kind of plain too, but has a basic HTML structure:

{# app/Resources/views/base.html.twig #}
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8" />
        <title>{% block title %}Welcome!{% endblock %}</title>
        {% block stylesheets %}{% endblock %}
        <link rel="icon" type="image/x-icon" href="{{ asset('favicon.ico') }}" />
    </head>
    <body>
        {% block body %}{% endblock %}
        {% block javascripts %}{% endblock %}
    </body>
</html>

To use this layout, we "extend" it. First, add the extends tag to the top of the index.html.twig template. Now, wrap everthing else in a {% block body %} tag:

{# src/Yoda/EventBundle/Resources/views/Default/index.html.twig #}
{% extends '::base.html.twig' %}

{% block body %}
    {# ... the rest of the template ... #}
{% endblock %}

Refresh and check out the source. The HTML from base.html.twig is being used and the content from our template is rendered in the middle of it.

Twig Blocks

Let's break this down. The extends tag says that we want to dress our template with another template. Inside base.html.twig, we have a bunch of block tags. One of them is called body and looks just like what we added to our template.

{# app/Resources/views/base.html.twig #}
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8" />
        <title>{% block title %}Welcome!{% endblock %}</title>
        {% block stylesheets %}{% endblock %}
        <link rel="icon" type="image/x-icon" href="{{ asset('favicon.ico') }}" />
    </head>
    <body>
        {% block body %}{% endblock %}
        {% block javascripts %}{% endblock %}
    </body>
</html>

Blocks define "holes" that a child template can fill in. The content in the body block of index.html.twig is inserted into the body block of base.html.twig.

There's also a title block, which already has content in it:

<title>{% block title %}Welcome!{% endblock %}</title>

This block has default content, which is working since the page's title is indeed Welcome!.

Let's replace it with something a bit less boring. We know how to do this now, just add a title block to index.html.twig.

{# src/Yoda/EventBundle/Resources/views/Default/index.html.twig #}
{% extends '::base.html.twig' %}

{% block title %}Some Twiggy Goodness{% endblock %}

{% block body %}
    {# ... #}
{% endblock %}

And to be even lazier, there's a shorter syntax for simple blocks like this:

{% block title 'Some Twiggy Goodness' %}

The blocks ones in base.html.twig are just suggestions, feel free to change their names or add some more to have an even more flexible layout.

Tip

Yes, you can also append to a block instead of replacing it. This is done with parent() and we chat about it in Episode 2.

"::base.html.twig" Naming

The ::base.html.twig filename looks weird. But it's actualy the exact same syntax we're using in our controller, just in disguise!

Remember that a template name always has three parts:

  • The bundle name
  • A subdirectory
  • And the template filename

In this case, the bundle name and subdirectory are just missing. When a template name has the bundle part, it means the template lives in the Resources/views directory of that bundle. But when this part is missing, like here, it means the template lives in the *app*/Resources/views directory. And since the second part is missing too, it means it lives directly there, and not in a subdirectory.

Tip

Template name and path examples

  • EventBundle:Default:index.html.twig

    src/Yoda/EventBundle/Resources/views/Default/index.html.twig

  • EventBundle::index.html.twig

    src/Yoda/EventBundle/Resources/views/index.html.twig

  • ::base.html.twig

    app/Resources/views/index.html.twig

Web Debug Toolbar

In the browser, we're now staring at a killer feature of Symfony2: the polite little bar on the bottom. This is the web debug toolbar, and you may end up loving it even more than the console.

It tells us which controller was rendered, the page load time, memory footprint, security info, form details and more. It's added automatically to any page that has a valid HTML structure. That's why we didn't see it until we extended the layout file.

Click anywhere on it to multiply the amount of information it gives you by 100! This is the profiler, which is broken down into sections. The best one is the Timeline. It visually tells us exactly what's going on during a request and how much time everything is taking. A lot of what you see here are background Symfony events.