Twig

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template engine for PHP

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License

Twig documentation is licensed under the new BSD license.

Twig for Template Designers

This document describes the syntax and semantics of the template engine and will be most useful as reference to those creating Twig templates.

Synopsis

A template is a regular text file. It can generate any text-based format (HTML, XML, CSV, LaTeX, etc.). It doesn't have a specific extension, .html or .xml are just fine.

A template contains variables or expressions, which get replaced with values when the template is evaluated, and tags, which control the template's logic.

Below is a minimal template that illustrates a few basics. We will cover further details later on:

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<!DOCTYPE html>
<html>
    <head>
        <title>My Webpage</title>
    </head>
    <body>
        <ul id="navigation">
        {% for item in navigation %}
            <li><a href="{{ item.href }}">{{ item.caption }}</a></li>
        {% endfor %}
        </ul>

        <h1>My Webpage</h1>
        {{ a_variable }}
    </body>
</html>

There are two kinds of delimiters: {% ... %} and {{ ... }}. The first one is used to execute statements such as for-loops, the latter outputs the result of an expression.

IDEs Integration

Many IDEs support syntax highlighting and auto-completion for Twig:

You might also be interested in:

  • TwigFiddle: an online service that allows you to execute Twig templates from a browser; it supports all versions of Twig
  • Twig Language Server: provides some language features like syntax highlighting, diagnostics, auto complete, ...

Variables

The application passes variables to the templates for manipulation in the template. Variables may have attributes or elements you can access, too. The visual representation of a variable depends heavily on the application providing it.

Use a dot (.) to access attributes of a variable (methods or properties of a PHP object, or items of a PHP array):

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{{ foo.bar }}

Note

It's important to know that the curly braces are not part of the variable but the print statement. When accessing variables inside tags, don't put the braces around them.

Implementation

For convenience's sake foo.bar does the following things on the PHP layer:

  • check if foo is an array and bar a valid element;
  • if not, and if foo is an object, check that bar is a valid property;
  • if not, and if foo is an object, check that bar is a valid method (even if bar is the constructor - use __construct() instead);
  • if not, and if foo is an object, check that getBar is a valid method;
  • if not, and if foo is an object, check that isBar is a valid method;
  • if not, and if foo is an object, check that hasBar is a valid method;
  • if not, return a null value.

Twig also supports a specific syntax for accessing items on PHP arrays, foo['bar']:

  • check if foo is an array and bar a valid element;
  • if not, return a null value.

If a variable or attribute does not exist, you will receive a null value when the strict_variables option is set to false; alternatively, if strict_variables is set, Twig will throw an error (see environment options).

Note

If you want to access a dynamic attribute of a variable, use the attribute function instead.

The attribute function is also useful when the attribute contains special characters (like - that would be interpreted as the minus operator):

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{# equivalent to the non-working foo.data-foo #}
{{ attribute(foo, 'data-foo') }}

Global Variables

The following variables are always available in templates:

  • _self: references the current template name;
  • _context: references the current context;
  • _charset: references the current charset.

Setting Variables

You can assign values to variables inside code blocks. Assignments use the set tag:

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{% set foo = 'foo' %}
{% set foo = [1, 2] %}
{% set foo = {'foo': 'bar'} %}

Filters

Variables can be modified by filters. Filters are separated from the variable by a pipe symbol (|). Multiple filters can be chained. The output of one filter is applied to the next.

The following example removes all HTML tags from the name and title-cases it:

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{{ name|striptags|title }}

Filters that accept arguments have parentheses around the arguments. This example joins the elements of a list by commas:

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{{ list|join(', ') }}

To apply a filter on a section of code, wrap it with the apply tag:

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{% apply upper %}
    This text becomes uppercase
{% endapply %}

Go to the filters page to learn more about built-in filters.

Note

The apply tag was introduced in Twig 2.9; use the filter tag with previous versions.

Functions

Functions can be called to generate content. Functions are called by their name followed by parentheses (()) and may have arguments.

For instance, the range function returns a list containing an arithmetic progression of integers:

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{% for i in range(0, 3) %}
    {{ i }},
{% endfor %}

Go to the functions page to learn more about the built-in functions.

Named Arguments

Named arguments are supported in functions, filters and tests.

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{% for i in range(low=1, high=10, step=2) %}
    {{ i }},
{% endfor %}

Using named arguments makes your templates more explicit about the meaning of the values you pass as arguments:

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{{ data|convert_encoding('UTF-8', 'iso-2022-jp') }}

{# versus #}

{{ data|convert_encoding(from='iso-2022-jp', to='UTF-8') }}

Named arguments also allow you to skip some arguments for which you don't want to change the default value:

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{# the first argument is the date format, which defaults to the global date format if null is passed #}
{{ "now"|date(null, "Europe/Paris") }}

{# or skip the format value by using a named argument for the time zone #}
{{ "now"|date(timezone="Europe/Paris") }}

You can also use both positional and named arguments in one call, in which case positional arguments must always come before named arguments:

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{{ "now"|date('d/m/Y H:i', timezone="Europe/Paris") }}

Tip

Each function and filter documentation page has a section where the names of all arguments are listed when supported.

Control Structure

A control structure refers to all those things that control the flow of a program - conditionals (i.e. if/elseif/else), for-loops, as well as things like blocks. Control structures appear inside {% ... %} blocks.

For example, to display a list of users provided in a variable called users, use the for tag:

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<h1>Members</h1>
<ul>
    {% for user in users %}
        <li>{{ user.username|e }}</li>
    {% endfor %}
</ul>

The if tag can be used to test an expression:

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{% if users|length > 0 %}
    <ul>
        {% for user in users %}
            <li>{{ user.username|e }}</li>
        {% endfor %}
    </ul>
{% endif %}

Go to the tags page to learn more about the built-in tags.

Comments

To comment-out part of a line in a template, use the comment syntax {# ... #}. This is useful for debugging or to add information for other template designers or yourself:

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{# note: disabled template because we no longer use this
    {% for user in users %}
        ...
    {% endfor %}
#}

Including other Templates

The include function is useful to include a template and return the rendered content of that template into the current one:

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{{ include('sidebar.html') }}

By default, included templates have access to the same context as the template which includes them. This means that any variable defined in the main template will be available in the included template too:

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{% for box in boxes %}
    {{ include('render_box.html') }}
{% endfor %}

The included template render_box.html is able to access the box variable.

The name of the template depends on the template loader. For instance, the \Twig\Loader\FilesystemLoader allows you to access other templates by giving the filename. You can access templates in subdirectories with a slash:

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{{ include('sections/articles/sidebar.html') }}

This behavior depends on the application embedding Twig.

Template Inheritance

The most powerful part of Twig is template inheritance. Template inheritance allows you to build a base "skeleton" template that contains all the common elements of your site and defines blocks that child templates can override.

It's easier to understand the concept by starting with an example.

Let's define a base template, base.html, which defines an HTML skeleton document that might be used for a two-column page:

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<!DOCTYPE html>
<html>
    <head>
        {% block head %}
            <link rel="stylesheet" href="style.css"/>
            <title>{% block title %}{% endblock %} - My Webpage</title>
        {% endblock %}
    </head>
    <body>
        <div id="content">{% block content %}{% endblock %}</div>
        <div id="footer">
            {% block footer %}
                &copy; Copyright 2011 by <a href="http://domain.invalid/">you</a>.
            {% endblock %}
        </div>
    </body>
</html>

In this example, the block tags define four blocks 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.

A child template might look like this:

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{% extends "base.html" %}

{% block title %}Index{% endblock %}
{% block head %}
    {{ parent() }}
    <style type="text/css">
        .important { color: #336699; }
    </style>
{% endblock %}
{% block content %}
    <h1>Index</h1>
    <p class="important">
        Welcome to my awesome homepage.
    </p>
{% endblock %}

The extends tag is the key here. It tells the template engine that this template "extends" another template. When the template system evaluates this template, first it locates the parent. The extends tag should be the first tag in the template.

Note that since the child template doesn't define the footer block, the value from the parent template is used instead.

It's possible to render the contents of the parent block by using the parent function. This gives back the results of the parent block:

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{% block sidebar %}
    <h3>Table Of Contents</h3>
    ...
    {{ parent() }}
{% endblock %}

Tip

The documentation page for the extends tag describes more advanced features like block nesting, scope, dynamic inheritance, and conditional inheritance.

Note

Twig also supports multiple inheritance via "horizontal reuse" with the help of the use tag.

HTML Escaping

When generating HTML from templates, there's always a risk that a variable will include characters that affect the resulting HTML. There are two approaches: manually escaping each variable or automatically escaping everything by default.

Twig supports both, automatic escaping is enabled by default.

The automatic escaping strategy can be configured via the autoescape option and defaults to html.

Working with Manual Escaping

If manual escaping is enabled, it is your responsibility to escape variables if needed. What to escape? Any variable that comes from an untrusted source.

Escaping works by using the escape or e filter:

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{{ user.username|e }}

By default, the escape filter uses the html strategy, but depending on the escaping context, you might want to explicitly use another strategy:

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{{ user.username|e('js') }}
{{ user.username|e('css') }}
{{ user.username|e('url') }}
{{ user.username|e('html_attr') }}

Working with Automatic Escaping

Whether automatic escaping is enabled or not, you can mark a section of a template to be escaped or not by using the autoescape tag:

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{% autoescape %}
    Everything will be automatically escaped in this block (using the HTML strategy)
{% endautoescape %}

By default, auto-escaping uses the html escaping strategy. If you output variables in other contexts, you need to explicitly escape them with the appropriate escaping strategy:

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{% autoescape 'js' %}
    Everything will be automatically escaped in this block (using the JS strategy)
{% endautoescape %}

Escaping

It is sometimes desirable or even necessary to have Twig ignore parts it would otherwise handle as variables or blocks. For example if the default syntax is used and you want to use {{ as raw string in the template and not start a variable you have to use a trick.

The easiest way is to output the variable delimiter ({{) by using a variable expression:

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{{ '{{' }}

For bigger sections it makes sense to mark a block verbatim.

Macros

Macros are comparable with functions in regular programming languages. They are useful to reuse HTML fragments to not repeat yourself. They are described in the macro tag documentation.

Expressions

Twig allows expressions everywhere.

Note

The operator precedence is as follows, with the lowest-precedence operators listed first: ?: (ternary operator), b-and, b-xor, b-or, or, and, ==, !=, <=>, <, >, >=, <=, in, matches, starts with, ends with, .., +, -, ~, *, /, //, %, is (tests), **, ??, | (filters), [], and .:

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{% set greeting = 'Hello ' %}
{% set name = 'Fabien' %}

{{ greeting ~ name|lower }}   {# Hello fabien #}

{# use parenthesis to change precedence #}
{{ (greeting ~ name)|lower }} {# hello fabien #}

Literals

The simplest form of expressions are literals. Literals are representations for PHP types such as strings, numbers, and arrays. The following literals exist:

  • "Hello World": Everything between two double or single quotes is a string. They are useful whenever you need a string in the template (for example as arguments to function calls, filters or just to extend or include a template). A string can contain a delimiter if it is preceded by a backslash (\) -- like in 'It\'s good'. If the string contains a backslash (e.g. 'c:\Program Files') escape it by doubling it (e.g. 'c:\\Program Files').
  • 42 / 42.23: Integers and floating point numbers are created by writing the number down. If a dot is present the number is a float, otherwise an integer.
  • ["foo", "bar"]: Arrays are defined by a sequence of expressions separated by a comma (,) and wrapped with squared brackets ([]).

  • {"foo": "bar"}: Hashes are defined by a list of keys and values separated by a comma (,) and wrapped with curly braces ({}):

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    {# keys as string #}
{ 'foo': 'foo', 'bar': 'bar' }

{# keys as names (equivalent to the previous hash) #}
{ foo: 'foo', bar: 'bar' }

{# keys as integer #}
{ 2: 'foo', 4: 'bar' }

{# keys can be omitted if it is the same as the variable name #}
{ foo }
{# is equivalent to the following #}
{ 'foo': foo }

{# keys as expressions (the expression must be enclosed into parentheses) #}
{% set foo = 'foo' %}
{ (foo): 'foo', (1 + 1): 'bar', (foo ~ 'b'): 'baz' }
  • true / false: true represents the true value, false represents the false value.
  • null: null represents no specific value. This is the value returned when a variable does not exist. none is an alias for null.

Arrays and hashes can be nested:

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{% set foo = [1, {"foo": "bar"}] %}

Tip

Using double-quoted or single-quoted strings has no impact on performance but string interpolation is only supported in double-quoted strings.

Math

Twig allows you to do math in templates; the following operators are supported:

  • +: Adds two numbers together (the operands are casted to numbers). {{ 1 + 1 }} is 2.
  • -: Subtracts the second number from the first one. {{ 3 - 2 }} is 1.
  • /: Divides two numbers. The returned value will be a floating point number. {{ 1 / 2 }} is {{ 0.5 }}.
  • %: Calculates the remainder of an integer division. {{ 11 % 7 }} is 4.
  • //: Divides two numbers and returns the floored integer result. {{ 20 // 7 }} is 2, {{ -20 // 7 }} is -3 (this is just syntactic sugar for the round filter).
  • *: Multiplies the left operand with the right one. {{ 2 * 2 }} would return 4.
  • **: Raises the left operand to the power of the right operand. {{ 2 ** 3 }} would return 8.

Logic

You can combine multiple expressions with the following operators:

  • and: Returns true if the left and the right operands are both true.
  • or: Returns true if the left or the right operand is true.
  • not: Negates a statement.
  • (expr): Groups an expression.

Note

Twig also supports bitwise operators (b-and, b-xor, and b-or).

Note

Operators are case sensitive.

Comparisons

The following comparison operators are supported in any expression: ==, !=, <, >, >=, and <=.

Check if a string starts with or ends with another string:

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{% if 'Fabien' starts with 'F' %}
{% endif %}

{% if 'Fabien' ends with 'n' %}
{% endif %}

Check that a string contains another string via the containment operator (see next section).

Note

For complex string comparisons, the matches operator allows you to use regular expressions:

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{% if phone matches '/^[\\d\\.]+$/' %}
{% endif %}

Containment Operator

The in operator performs containment test. It returns true if the left operand is contained in the right:

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{# returns true #}

{{ 1 in [1, 2, 3] }}

{{ 'cd' in 'abcde' }}

Tip

You can use this filter to perform a containment test on strings, arrays, or objects implementing the Traversable interface.

To perform a negative test, use the not in operator:

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{% if 1 not in [1, 2, 3] %}

{# is equivalent to #}
{% if not (1 in [1, 2, 3]) %}

Test Operator

The is operator performs tests. Tests can be used to test a variable against a common expression. The right operand is name of the test:

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{# find out if a variable is odd #}

{{ name is odd }}

Tests can accept arguments too:

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{% if post.status is constant('Post::PUBLISHED') %}

Tests can be negated by using the is not operator:

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{% if post.status is not constant('Post::PUBLISHED') %}

{# is equivalent to #}
{% if not (post.status is constant('Post::PUBLISHED')) %}

Go to the tests page to learn more about the built-in tests.

Other Operators

The following operators don't fit into any of the other categories:

  • |: Applies a filter.

  • ..: Creates a sequence based on the operand before and after the operator (this is syntactic sugar for the range function):

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    {{ 1..5 }}

{# equivalent to #}
{{ range(1, 5) }}

    Note that you must use parentheses when combining it with the filter operator due to the operator precedence rules:

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    (1..5)|join(', ')
  • ~: Converts all operands into strings and concatenates them. {{ "Hello " ~ name ~ "!" }} would return (assuming name is 'John') Hello John!.
  • ., []: Gets an attribute of a variable.

  • ?:: The ternary operator:

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    {{ foo ? 'yes' : 'no' }}
{{ foo ?: 'no' }} is the same as {{ foo ? foo : 'no' }}
{{ foo ? 'yes' }} is the same as {{ foo ? 'yes' : '' }}

  • ??: The null-coalescing operator:

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    {# returns the value of foo if it is defined and not null, 'no' otherwise #}
{{ foo ?? 'no' }}

String Interpolation

String interpolation (#{expression}) allows any valid expression to appear within a double-quoted string. The result of evaluating that expression is inserted into the string:

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{{ "foo #{bar} baz" }}
{{ "foo #{1 + 2} baz" }}

Whitespace Control

2.8

Tag level line whitespace control was added in Twig 2.8.

The first newline after a template tag is removed automatically (like in PHP). Whitespace is not further modified by the template engine, so each whitespace (spaces, tabs, newlines etc.) is returned unchanged.

You can also control whitespace on a per tag level. By using the whitespace control modifiers on your tags, you can trim leading and or trailing whitespace.

Twig supports two modifiers:

  • Whitespace trimming via the - modifier: Removes all whitespace (including newlines);
  • Line whitespace trimming via the ~ modifier: Removes all whitespace (excluding newlines). Using this modifier on the right disables the default removal of the first newline inherited from PHP.

The modifiers can be used on either side of the tags like in {%- or -%} and they consume all whitespace for that side of the tag. It is possible to use the modifiers on one side of a tag or on both sides:

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{% set value = 'no spaces' %}
{#- No leading/trailing whitespace -#}
{%- if true -%}
    {{- value -}}
{%- endif -%}
{# output 'no spaces' #}

<li>
    {{ value }}    </li>
{# outputs '<li>\n    no spaces    </li>' #}

<li>
    {{- value }}    </li>
{# outputs '<li>no spaces    </li>' #}

<li>
    {{~ value }}    </li>
{# outputs '<li>\nno spaces    </li>' #}

Tip

In addition to the whitespace modifiers, Twig also has a spaceless filter that removes whitespace between HTML tags:

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{% apply spaceless %}
    <div>
        <strong>foo bar</strong>
    </div>
{% endapply %}

{# output will be <div><strong>foo bar</strong></div> #}

The apply tag was introduced in Twig 2.9; use the filter tag with previous versions.

Extensions

Twig can be extended. If you want to create your own extensions, read the Creating an Extension chapter.

« Installation | Twig for Developers »