Twig for Developers

Compilation Cache

All template loaders can cache the compiled templates on the filesystem for future reuse. It speeds up Twig a lot as templates are only compiled once.

Built-in Loaders

Here is a list of the built-in loaders:

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$loader = new \Twig\Loader\FilesystemLoader($templateDir);

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$loader = new \Twig\Loader\FilesystemLoader([$templateDir1, $templateDir2]);

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$loader->addPath($templateDir3);
$loader->prependPath($templateDir4);

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$loader->addPath($templateDir, 'admin');

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$twig->render('@admin/index.html', []);

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$loader = new \Twig\Loader\FilesystemLoader('templates', getcwd().'/..');

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$loader = new \Twig\Loader\ArrayLoader([
    'index.html' => 'Hello {{ name }}!',
]);
$twig = new \Twig\Environment($loader);

echo $twig->render('index.html', ['name' => 'Fabien']);

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$loader1 = new \Twig\Loader\ArrayLoader([
    'base.html' => '{% block content %}{% endblock %}',
]);
$loader2 = new \Twig\Loader\ArrayLoader([
    'index.html' => '{% extends "base.html" %}{% block content %}Hello {{ name }}{% endblock %}',
    'base.html'  => 'Will never be loaded',
]);

$loader = new \Twig\Loader\ChainLoader([$loader1, $loader2]);

$twig = new \Twig\Environment($loader);

Create your own Loader

All loaders implement the \Twig\Loader\LoaderInterface:

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interface \Twig\Loader\LoaderInterface
{
    /**
     * Returns the source context for a given template logical name.
     *
     * @param string $name The template logical name
     *
     * @return \Twig\Source
     *
     * @throws \Twig\Error\LoaderError When $name is not found
     */
    public function getSourceContext($name);

    /**
     * Gets the cache key to use for the cache for a given template name.
     *
     * @param string $name The name of the template to load
     *
     * @return string The cache key
     *
     * @throws \Twig\Error\LoaderError When $name is not found
     */
    public function getCacheKey($name);

    /**
     * Returns true if the template is still fresh.
     *
     * @param string    $name The template name
     * @param timestamp $time The last modification time of the cached template
     *
     * @return bool    true if the template is fresh, false otherwise
     *
     * @throws \Twig\Error\LoaderError When $name is not found
     */
    public function isFresh($name, $time);

    /**
     * Check if we have the source code of a template, given its name.
     *
     * @param string $name The name of the template to check if we can load
     *
     * @return bool    If the template source code is handled by this loader or not
     */
    public function exists($name);
}

The isFresh() method must return true if the current cached template is still fresh, given the last modification time, or false otherwise.

The getSourceContext() method must return an instance of \Twig\Source.

Core Extension

The core extension defines all the core features of Twig:

• Tags;
• Filters;
• Functions;
• Tests.

Escaper Extension

The escaper extension adds automatic output escaping to Twig. It defines a tag, autoescape, and a filter, raw.

When creating the escaper extension, you can switch on or off the global output escaping strategy:

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$escaper = new \Twig\Extension\EscaperExtension('html');
$twig->addExtension($escaper);

If set to html, all variables in templates are escaped (using the html escaping strategy), except those using the raw filter:

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{{ article.to_html|raw }}

You can also change the escaping mode locally by using the autoescape tag:

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{% autoescape 'html' %}
    {{ var }}
    {{ var|raw }}      {# var won't be escaped #}
    {{ var|escape }}   {# var won't be double-escaped #}
{% endautoescape %}

The escaping rules are implemented as follows:

• Literals (integers, booleans, arrays, ...) used in the template directly as variables or filter arguments are never automatically escaped:

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  {{ "Twig<br/>" }} {# won't be escaped #}
  
  {% set text = "Twig<br/>" %}
  {{ text }} {# will be escaped #}

• Expressions which the result is a literal or a variable marked safe are never automatically escaped:

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  {{ any_value ? "Twig<br/>" : "<br/>Twig" }} {# won't be escaped #}
  
  {% set text = "Twig<br/>" %}
  {{ true ? text : "<br/>Twig" }} {# will be escaped #}
  {{ false ? text : "<br/>Twig" }} {# won't be escaped #}
  
  {% set text = "Twig<br/>" %}
  {{ any_value ? text|raw : "<br/>Twig" }} {# won't be escaped #}

• Objects with a __toString method are converted to strings and escaped. You can mark some classes and/or interfaces as being safe for some strategies via EscaperExtension::addSafeClass():

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  // mark objects of class "HtmlGenerator" as safe for the HTML strategy
  $escaper->addSafeClass('HtmlGenerator', ['html']);
  
  // mark objects of interface "HtmlGeneratorInterface" as safe for the HTML strategy
  $escaper->addSafeClass('HtmlGeneratorInterface', ['html']);
  
  // mark objects of class "HtmlGenerator" as safe for the HTML and JS strategies
  $escaper->addSafeClass('HtmlGenerator', ['html', 'js']);
  
  // mark objects of class "HtmlGenerator" as safe for all strategies
  $escaper->addSafeClass('HtmlGenerator', ['all']);

• Escaping is applied before printing, after any other filter is applied:

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  {{ var|upper }} {# is equivalent to {{ var|upper|escape }} #}

• The raw filter should only be used at the end of the filter chain:

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  {{ var|raw|upper }} {# will be escaped #}
  
  {{ var|upper|raw }} {# won't be escaped #}

• Automatic escaping is not applied if the last filter in the chain is marked safe for the current context (e.g. html or js). escape and escape('html') are marked safe for HTML, escape('js') is marked safe for JavaScript, raw is marked safe for everything.

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  {% autoescape 'js' %}
      {{ var|escape('html') }} {# will be escaped for HTML and JavaScript #}
      {{ var }} {# will be escaped for JavaScript #}
      {{ var|escape('js') }} {# won't be double-escaped #}
  {% endautoescape %}

Sandbox Extension

The sandbox extension can be used to evaluate untrusted code. Read more about it in the Twig Sandbox chapter.

Profiler Extension

The profiler extension enables a profiler for Twig templates; it should only be used on your development machines as it adds some overhead:

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$profile = new \Twig\Profiler\Profile();
$twig->addExtension(new \Twig\Extension\ProfilerExtension($profile));

$dumper = new \Twig\Profiler\Dumper\TextDumper();
echo $dumper->dump($profile);

A profile contains information about time and memory consumption for template, block, and macro executions.

You can also dump the data in a Blackfire.io compatible format:

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$dumper = new \Twig\Profiler\Dumper\BlackfireDumper();
file_put_contents('/path/to/profile.prof', $dumper->dump($profile));

Upload the profile to visualize it (create a free account first):

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blackfire --slot=7 upload /path/to/profile.prof

Optimizer Extension

The optimizer extension optimizes the node tree before compilation:

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$twig->addExtension(new \Twig\Extension\OptimizerExtension());

By default, all optimizations are turned on. You can select the ones you want to enable by passing them to the constructor:

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$optimizer = new \Twig\Extension\OptimizerExtension(\Twig\NodeVisitor\OptimizerNodeVisitor::OPTIMIZE_FOR);

$twig->addExtension($optimizer);

Twig supports the following optimizations:

• \Twig\NodeVisitor\OptimizerNodeVisitor::OPTIMIZE_ALL, enables all optimizations (this is the default value).
• \Twig\NodeVisitor\OptimizerNodeVisitor::OPTIMIZE_NONE, disables all optimizations. This reduces the compilation time, but it can increase the execution time and the consumed memory.
• \Twig\NodeVisitor\OptimizerNodeVisitor::OPTIMIZE_FOR, optimizes the for tag by removing the loop variable creation whenever possible.