Introduction to Twig

TWIG

Saturday, 3 November, 12

ABOUT ME

Team lead at FreshBooks

Lead Developer of CakePHP

Contributor to Twig


WHAT IS IT

Templating language for PHP.

Uses syntax and ideas from jinja2.

Flexible and extensible at every layer.


BUT PHP IS A
TEMPLATING
LANGUAGE DUMMY


PHP SUCKS FOR TEMPLATING
// In Plain PHP
<?php echo $var; ?> (XSS you lose)
<?php echo htmlspecialchars($var, ENT_QUOTES, ‘UTF-8’); ?>
<?php echo h($var); ?> (sugar for htmlentities)

// In Twig - autoescaping enabled
{{ var }}


BENEFITS OF TWIG

Terse syntax, and sugar.

Automatic HTML escaping.

Sandbox mode, which enables user editable templates.

Ability to create custom DSL’s using application tags, operators
and functions.


PLAIN PHP VS TWIG


CONDITIONALS

// In Plain PHP
<?php if (!empty($var): ?>
...
<?php endif; ?>

// In Twig
{% if var %}
...
{% endif %}


LOOPS

<?php
if (!empty($var):
foreach ((array)$var as $i => $v):
printf(
‘%s : %s’,
htmlspecialchars($i, ENT_QUOTES, ‘UTF-8’),
htmlspecialchars($v, ENT_QUOTES, ‘UTF-8’));
endforeach;
else:
echo ‘No things’;
endif;


LOOPS

{% for i, v in var %}
{{ i }} : {{ v }}
{% else %}
No things
{% endfor %}


LOOPS

{% for user in users if user.active %}
{{ user.name }} : {{ user.email }}
{% else %}
No active users
{% endfor %}


BUT WAIT THERE IS
MORE


AWESOME++

Macros.

Blocks & extending templates.


MACROS

{% macro username(user) %}
<a href=”{{ url({
‘controller’: ‘users’,
‘action’: ‘view’,
user.username) }}”>
<span class=”user-first-name”>
{{ user.first_name }}
</span>
<span> class=”user-last-name”>
{{ user.last_name }}
</span>
</a>
{% endmacro %}


IMPORTING MACROS

// import all the macros
{% import ‘/import/formatting.twig’ as formatting %}
{{ formatting.username(user) }}

// import one macro
{% from ‘/import/formatting.twig’ import username %}
{{ username(user) }}

// import one & alias it.
{% from ‘/import/formatting.twig’ import username as un %}
{{ un(user) }}


INHERITANCE & BLOCKS

Extending views & blocks work hand in hand.

Blocks are like slots or holes in a template, that the child can ﬁll.

Blocks can be used out of order, which is pretty sweet.

Blocks can be imported from other templates, similar to traits.


INHERITANCE

{# layout/base.twig #}

Company X - Official Email template

{% block content ‘Super important’ %}

Copyright 2012


INHERITANCE

{# email/winner.twig #}
{% extend ‘/layout/base.twig’ %}

{% block content %}
To whom it may concern,

You win!
{% endblock %}


INHERITANCE

{# email/winner.twig #}
{% extend ‘/layout/base.twig’ %}

{% block content %}
To whom it may concern,

{{ parent() }} You win!

{% endblock %}


INHERITANCE TIPS

Don’t use {% block %} inside a loop. It doesn’t do what you
want.

You can use {{ block(name) }} to dynamically call blocks.


EXTENDING TWIG
TWIG EXTENSIONS


EXTENDING TWIG

Twig can be extended in several ways.

Filters, Functions, Globals, Tests, Operators, TokenParsers,
NodeVisitors.

You should use extensions to package up your enhancements.


TWIG EXTENSIONS


LOADING EXTENSIONS

$loader = new Twig_Loader_FileSystem(APP . ‘/templates’);
$twig = new Twig_Environment($loader, $options);
$twig->addExtension(new App_Extension_Url());


ENVIRONMENT FACTORY

class AppTwig {
static function loadTemplate($template, $options = array()) {
$loader = new Twig_Loader_FileSystem(APP . ‘/templates’);
$twig = new Twig_Environment($loader, $options);
$twig->addExtension(new App_Extension_Url());
// Load more extensions
return $twig->loadTemplate($template);
}
}

$template = AppTwig::loadTemplate(‘/users/profile.twig’);


EXTENSION EXAMPLE
<?php
class App_Extension_Url extends Twig_Extension {
public function getName() {
return ‘app.url’;
}

public function getFilters() {
return array(
‘name’ => new Twig_Filter_Method($this, ‘formatName’),
);
}
}


GLOBALS

Can be used to expose application or framework objects.

Great for migrating an older codebase to use Twig.

E.g {{ html.link(...) }}


FUNCTIONS

Global functions added to a template context.

Great for providing shortcuts to application features, like url
generation or built-in PHP functions.

Example {{ form_input(model, ‘name’) }}


FILTERS

Filters are intended for simple formatting functions.

The filtered variable is the first argument to the filter function.

Filters can have additional arguments as well.

Example: {{ invoice.amount|currency(‘CAD’) }}


TESTS

Allow you to implement custom conditional logic. In an
expressive manner with domain objects.

Value being compared is supplied as the ﬁrst argument. Other
arguments follow.

{% if user is paying %}
{% if number is divisibleby(3) %}


NODE VISITORS

Allows you to visit each node in the Abstract syntax tree.

Applied before template is compiled.

Commonly used for optimizing the AST, or applying
transformations to, or reading data from nodes in the tree.


CUSTOM TAGS


TWIG INTERNALS

ENVIRONMENT

LOADER


TWIG INTERNALS

ENVIRONMENT LEXER

LOADER


TWIG INTERNALS

ENVIRONMENT LEXER

LOADER TOKENS


TWIG INTERNALS

ENVIRONMENT LEXER PARSER

LOADER TOKENS


TWIG INTERNALS

ENVIRONMENT LEXER PARSER

LOADER TOKENS NODES


TWIG INTERNALS

ENVIRONMENT LEXER PARSER COMPILER

LOADER TOKENS NODES


TWIG INTERNALS

ENVIRONMENT LEXER PARSER COMPILER

LOADER TOKENS NODES

PHP CODE


TOKEN PARSERS

Used to implement custom tags or DSL features.

The most complex feature to add.

Each tag is composed of two parts:

TokenParser - parses the tag and validates its syntax.

Node - Added to the AST and compiles the PHP code used
in templates.


TAG EXAMPLE

{% debug %}

{% debug my_var %}

{% debug 2 > 1 %}


TOKEN PARSER
class App_TokenParser_Debug extends Twig_TokenParser {

public function parse(Twig_Token $token) {
$line = $token->getLine();
$expr = null;
if (!$this->parser->getStream()->test(Twig_Token::BLOCK_END_TYPE)) {
$expr = $this->parser->getExpressionParser->parseExpression();
}
$this->parse->getStream()->expect(Twig_Token::BLOCK_END_TYPE);
return new App_Node_Debug($expr, $line, $this->getTag());
}

}


NODE COMPILER
class App_Node_Debug extends Twig_Node {

public function __construct(Twig_Node_Expression $ex, $line, $tag) {
parent::__construct(array(‘expr’ => $ex), $line, $tag);
}

public function compile(Twig_Compiler $compiler) {
$compiler->write(‘if ($this->env->isDebug()) {‘);
if ($this->getNode(‘expr’) === null) {
// Print all vars.
} else {
$compiler->write(‘var_dump(‘)
->subcompile($this->getNode(‘expr’))
->raw(‘);’);
}
$compiler->write(‘}’);
}

}


OPERATORS

Allow you to add additional boolean operators.

I’ve never used this feature.


DEPLOYING TWIG


TWIG IN PRODUCTION

FreshBooks (the app, not the website).

520+ templates.

Twig templates are used for almost all HTML & E-mail content.


TEMPLATE COMPILATION

TWIG



TWIG PHP



TWIG PHP HTML



TWIG PHP HTML

Saved to disk



PHP HTML

Saved to disk


HOW WE DEPLOY


HOW WE DEPLOY

COPY
FILES


HOW WE DEPLOY

COPY COMPILE
FILES / BUILD


HOW WE DEPLOY

COPY COMPILE
SYMLINK
FILES / BUILD


PRECOMPILE SCRIPT
$directory = new RecursiveDirectoryIterator($argv[0]);
$recurser = new RecursiveIteratorIterator($directory);
$matcher = new RegexIterator(
$recurser,
'/.*?.twig$/',
RegexIterator::GET_MATCH);

echo "Compiling Templatesn";

$i = 0;
foreach ($matcher as $file) {
$filename = str_replace($argv[1], '', $file[0]);
AppTwig::loadTemplate('/' . $filename);
echo '.';
$i++;
}
echo "nTemplates compiledn";
exit(0);


TWIG C EXTENSION

You can also install ext/twig.

This pushes the most frequently used method
Twig_Template::getAttribute() into C which increases
performance considerably.

The C extension is in the Twig repository.


QUESTIONS?


THANKS
@MARK_STORY
HTTP://MARK-STORY.COM


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