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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:

.. code-block:: html+twig

    <!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.

.. tip::

    To experiment with Twig, you can use the `Twig Playground
    <https://twig.symfony.com/play>`_.

Third-party Integrations
------------------------

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

* *Textmate* via the `Twig bundle`_
* *Vim* via the `vim-twig plugin`_
* *Netbeans* (native as of 7.2)
* *PhpStorm* (native as of 2.1)
* *Eclipse* via the `Twig plugin`_
* *Sublime Text* via the `Twig bundle`_
* *GtkSourceView* via the `Twig language definition`_ (used by gedit and other projects)
* *Coda* and *SubEthaEdit* via the `Twig syntax mode`_
* *Coda 2* via the `other Twig syntax mode`_
* *Komodo* and *Komodo Edit* via the Twig highlight/syntax check mode
* *Notepad++* via the `Notepad++ Twig Highlighter`_
* *Emacs* via `web-mode.el`_
* *Atom* via the `PHP-twig for atom`_
* *Visual Studio Code* via the `Twig pack`_, `Modern Twig`_ or `Twiggy`_

You might also be interested in:

* `Twig Language Server`_: provides some language features like syntax
  highlighting, diagnostics, auto complete, ...

* `TwigQI`_: an extension which analyzes your templates for common bugs during compilation

* `TwigStan`_: a static analyzer for Twig templates powered by PHPStan

Variables
---------

Twig templates have access to variables provided by the PHP application and
variables created in templates via the :doc:`set <tags/set>` tag. These
variables can be manipulated and displayed in the template.

Twig tries to abstract PHP types as much as possible and works with a few basic
types, supported by ``filters``, ``functions``, and ``tests`` among others:

===================  ===============================
Twig Type            PHP Type
===================  ===============================
string               A string or a Stringable object
number               An integer or a float
boolean              ``true`` or ``false``
null                 ``null``
iterable (mapping)   An array
iterable (sequence)  An array
iterable (object)    An iterable object
object               An object
===================  ===============================

The ``iterable`` and ``object`` types expose attributes you can access via the
dot (``.``) operator:

.. code-block:: twig

    {{ user.name }}

.. 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.

If a variable or attribute does not exist, the behavior depends on the
``strict_variables`` option value (see :ref:`environment options
<environment_options_strict_variables>`):

* When ``false``, it returns ``null``;
* When ``true``, it throws an exception.

Learn more about the :ref:`dot operator <dot_operator>`.

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
:doc:`set<tags/set>` tag:

.. code-block:: twig

    {% set name = 'Fabien' %}
    {% set numbers = [1, 2] %}
    {% set map = {'city': 'Paris'} %}

Filters
-------

Variables and expressions 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:

.. code-block:: twig

    {{ name|striptags|title }}

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

.. code-block:: twig

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

To apply a filter on a section of code, wrap it with the
:doc:`apply<tags/apply>` tag:

.. code-block:: twig

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

Go to the :doc:`filters<filters/index>` page to learn more about built-in
filters.

.. warning::

    As the ``filter`` operator has the highest :ref:`precedence
    <twig-expressions>`, use parentheses when filtering more "complex"
    expressions:

    .. code-block:: twig

        {{ (1..5)|join(', ') }}

        {{ ('HELLO' ~ 'FABIEN')|lower }}

    A common mistake is to forget using parentheses for filters on negative
    numbers as a negative number in Twig is represented by the ``-`` operator
    followed by a positive number. As the ``-`` operator has a lower precedence
    than the filter operator, it can lead to confusion:

    .. code-block:: twig

        {{ -1|abs }} {# returns -1 #}
        {{ -1**0 }} {# returns -1 #}

        {# as it is equivalent to #}

        {{ -(1|abs) }}
        {{ -(1**0) }}

    For such cases, use parentheses to force the precedence:

    .. code-block:: twig

        {{ (-1)|abs }} {# returns 1 as expected #}
        {{ (-1)**0 }} {# returns 1 as expected #}

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:

.. code-block:: twig

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

Go to the :doc:`functions<functions/index>` page to learn more about the
built-in functions.

.. _named-arguments:

Named Arguments
---------------

Named arguments are supported everywhere you can pass arguments: functions,
filters, tests, macros, and dot operator arguments.

.. versionadded:: 3.15

    Named arguments for macros and dot operator arguments were added in Twig
    3.15.

.. versionadded:: 3.12

    Twig supports both ``=`` and ``:`` as separators between argument names and
    values, but support for ``:`` was introduced in Twig 3.12.

.. code-block:: twig

    {% 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:

.. code-block:: twig

    {{ 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:

.. code-block:: twig

    {# 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:

.. code-block:: twig

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

.. tip::

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

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 :doc:`for<tags/for>` tag:

.. code-block:: html+twig

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

The :doc:`if<tags/if>` tag can be used to test an expression:

.. code-block:: html+twig

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

Go to the :doc:`tags<tags/index>` page to learn more about the built-in tags.

Comments
--------

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

.. code-block:: twig

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

.. versionadded:: 3.15

    Inline comments were added in Twig 3.15.

If you want to add comments inside a block, variable, or comment, use an inline
comment. They start with ``#`` and continue to the end of the line:

.. code-block:: twig

    {{
        # this is an inline comment
        "Hello World"|upper
        # this is an inline comment
    }}

    {{
        {
            # this is an inline comment
            fruit: 'apple', # this is an inline comment
            color: 'red', # this is an inline comment
        }|join(', ')
    }}

Inline comments can also be on the same line as the expression:

.. code-block:: twig

    {{
        "Hello World"|upper # this is an inline comment
    }}

As inline comments continue until the end of the current line, the following
code does not work as ``}}``would be part of the comment:

.. code-block:: twig

    {{ "Hello World"|upper # this is an inline comment }}

Including other Templates
-------------------------

The :doc:`include<functions/include>` function is useful to include a template
and return the rendered content of that template into the current one:

.. code-block:: twig

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

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:

.. code-block:: twig

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

The included template ``render_box.html.twig`` 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:

.. code-block:: twig

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

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.twig``, which defines an HTML skeleton
document that might be used for a two-column page:

.. code-block:: html+twig

    <!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="https://example.com/">you</a>.
                {% endblock %}
            </div>
        </body>
    </html>

In this example, the :doc:`block<tags/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:

.. code-block:: html+twig

    {% extends "base.html.twig" %}

    {% 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 :doc:`extends<tags/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
:doc:`parent<functions/parent>` function. This gives back the results of the
parent block:

.. code-block:: html+twig

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

.. tip::

    The documentation page for the :doc:`extends<tags/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 :doc:`use<tags/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
:ref:`autoescape<environment_options>` 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 :doc:`escape<filters/escape>` or ``e`` filter:

.. code-block:: twig

    {{ 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:

.. code-block:: twig

    {{ 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 :doc:`autoescape<tags/autoescape>`
tag:

.. code-block:: twig

    {% 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:

.. code-block:: twig

    {% 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:

.. code-block:: twig

    {{ '{{' }}

For bigger sections it makes sense to mark a block
:doc:`verbatim<tags/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
:doc:`macro<tags/macro>` tag documentation.

.. _twig-expressions:

Expressions
-----------

Twig allows expressions everywhere.

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).

  Note that certain characters require escaping:
   * ``\f``: Form feed
   * ``\n``: New line
   * ``\r``: Carriage return
   * ``\t``: Horizontal tab
   * ``\v``: Vertical tab
   * ``\x``: Hexadecimal escape sequence
   * ``\0`` to ``\377``: Octal escape sequences representing characters
   * ``\``: Backslash

   When using single-quoted strings, the single quote character (``'``) needs to be escaped with a backslash (``\'``).
   When using double-quoted strings, the double quote character (``"``) needs to be escaped with a backslash (``\"``).

   For example, a single quoted 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. Underscores can be used as digits separator to 
  improve readability (``-3_141.592_65`` is equivalent to ``-3141.59265``).

* ``["first_name", "last_name"]``: Sequences are defined by a sequence of expressions
  separated by a comma (``,``) and wrapped with squared brackets (``[]``).

* ``{"name": "Fabien"}``: Mappings are defined by a list of keys and values
  separated by a comma (``,``) and wrapped with curly braces (``{}``):

  .. code-block:: twig

    {# keys as string #}
    {'name': 'Fabien', 'city': 'Paris'}

    {# keys as names (equivalent to the previous mapping) #}
    {name: 'Fabien', city: 'Paris'}

    {# keys as integer #}
    {2: 'Twig', 4: 'Symfony'}

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

    {# keys as expressions (the expression must be enclosed into parentheses) #}
    {% set key = 'name' %}
    {(key): 'Fabien', (1 + 1): 2, ('ci' ~ 'ty'): 'city'}

* ``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``.

Sequences and mappings can be nested:

.. code-block:: twig

    {% set complex = [1, {"name": "Fabien"}] %}

.. tip::

    Using double-quoted or single-quoted strings has no impact on performance
    but :ref:`string interpolation <templates-string-interpolation>` is only
    supported in double-quoted strings.

.. _templates-string-interpolation:

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:

.. code-block:: twig

    {{ "first #{middle} last" }}
    {{ "first #{1 + 2} last" }}

.. tip::

    String interpolations can be ignored by escaping them with a backslash
    (``\``):

    .. code-block:: twig

        {# outputs first #{1 + 2} last #}
        {{ "first \#{1 + 2} last" }}

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 :doc:`round<filters/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``.

.. _template_logic:

Logic
~~~~~

You can combine multiple expressions with the following operators:

* ``and``: Returns true if the left and the right operands are both true.

* ``xor``: Returns true if **either** the left or the right operand is true, but not both.

* ``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 mathematical comparison operators are supported in any
expression: ``==``, ``!=``, ``<``, ``>``, ``>=``, and ``<=``.

Spaceship Operator
~~~~~~~~~~~~~~~~~~

The spaceship operator (``<=>``) is used for comparing two expressions. It
returns ``-1``, ``0`` or ``1`` when the first operand is respectively less
than, equal to, or greater than the second operand.

.. note::

    Read more about in the `PHP spaceship operator documentation`_.

Iterable Operators
~~~~~~~~~~~~~~~~~~

Check that an iterable ``has every`` or ``has some`` of its elements return
``true`` using an arrow function. The arrow function receives the value of the
iterable as its argument:

.. code-block:: twig

    {% set sizes = [34, 36, 38, 40, 42] %}

    {% set hasOnlyOver38 = sizes has every v => v > 38 %}
    {# hasOnlyOver38 is false #}

    {% set hasOver38 = sizes has some v => v > 38 %}
    {# hasOver38 is true #}

For an empty iterable, ``has every`` returns ``true`` and ``has some`` returns
``false``.

Containment Operators
~~~~~~~~~~~~~~~~~~~~~

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

.. code-block:: twig

    {# returns true #}

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

    {{ 'cd' in 'abcde' }}

.. tip::

    You can use this operator to perform a containment test on strings,
    sequences, mappings, or objects implementing the ``Traversable`` interface.

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

.. code-block:: twig

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

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

The ``starts with`` and ``ends with`` operators are used to check if a string
starts or ends with a given substring:

.. code-block:: twig

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

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

.. note::

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

    .. code-block:: twig

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

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:

.. code-block:: twig

    {# find out if a variable is odd #}

    {{ name is odd }}

Tests can accept arguments too:

.. code-block:: twig

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

Tests can be negated by using the ``is not`` operator:

.. code-block:: twig

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

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

Go to the :doc:`tests<tests/index>` 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 :doc:`range<functions/range>` function):

  .. code-block:: twig

      {% for i in 1..5 %}{{ i }}{% endfor %}

      {# is equivalent to #}
      {% for i in range(1, 5) %}{{ i }}{% endfor %}

  Note that you must use parentheses when combining it with the filter operator
  due to the :ref:`operator precedence rules <twig-expressions>`:

  .. code-block:: twig

      {{ (1..5)|join(', ') }}

* ``~``: Converts all operands into strings and concatenates them. ``{{ "Hello
  " ~ name ~ "!" }}`` would return (assuming ``name`` is ``'John'``) ``Hello
  John!``.

.. _dot_operator:

* ``.``, ``[]``: Gets an attribute of a variable.

  The (``.``) operator abstracts getting an attribute of a variable (methods,
  properties or constants of a PHP object, or items of a PHP array):

  .. code-block:: twig

      {{ user.name }}

      Twig supports a specific syntax via the ``[]`` operator for accessing items
      on sequences and mappings, like in ``user['name']``:

  After the ``.``, you can use any expression by wrapping it with parenthesis
  ``()``.

  One use case is when the attribute contains special characters (like ``-``
  that would be interpreted as the minus operator):

  .. code-block:: twig

      {# equivalent to the non-working user.first-name #}
      {{ user.('first-name') }}

  Another use case is when the attribute is "dynamic" (defined via a variable):

  .. code-block:: twig

      {{ user.(name) }}
      {{ user.('get' ~ name) }}

  Before Twig 3.15, use the :doc:`attribute <functions/attribute>` function
  instead for the two previous use cases.

  Twig supports a specific syntax via the ``[]`` operator for accessing items
  on sequences and mappings:

  .. code-block:: twig

      {{ user['name'] }}

  When calling a method, you can pass arguments using the ``()`` operator:

  .. code-block:: twig

      {{ html.generate_input() }}
      {{ html.generate_input('pwd', 'password') }}
      {# or using named arguments #}
      {{ html.generate_input(name: 'pwd', type: 'password') }}

  .. sidebar:: PHP Implementation

      To resolve ``user.name`` to a PHP call, Twig uses the following algorithm
      at runtime:

      * check if ``user`` is a PHP array or a ArrayObject/ArrayAccess object and
        ``name`` a valid element;
      * if not, and if ``user`` is a PHP object, check that ``name`` is a valid property;
      * if not, and if ``user`` is a PHP object, check that ``name`` is a class constant;
      * if not, and if ``user`` is a PHP object, check the following methods and
        call the first valid one: ``name()``, ``getName()``, ``isName()``, or
        ``hasName()``;
      * if not, and if ``strict_variables`` is ``false``, return ``null``;
      * if not, throw an exception.

      To resolve ``user['name']`` to a PHP call, Twig uses the following algorithm
      at runtime:

      * check if ``user`` is an array and ``name`` a valid element;
      * if not, and if ``strict_variables`` is ``false``, return ``null``;
      * if not, throw an exception.

      Twig supports a specific syntax via the ``()`` operator for calling methods
      on objects, like in ``user.name()``:

      * check if ``user`` is a object and has the ``name()``, ``getName()``,
        ``isName()``, or ``hasName()`` method;
      * if not, and if ``strict_variables`` is ``false``, return ``null``;
      * if not, throw an exception.

* ``?:``: The ternary operator:

  .. code-block:: twig

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

* ``??``: The null-coalescing operator:

  .. code-block:: twig

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

* ``...``: The spread operator can be used to expand sequences or mappings or
  to expand the arguments of a function call:

  .. code-block:: twig

      {% set numbers = [1, 2, ...moreNumbers] %}
      {% set ratings = {'q1': 10, 'q2': 5, ...moreRatings} %}

      {{ 'Hello %s %s!'|format(...['Fabien', 'Potencier']) }}

  .. versionadded:: 3.15

    Support for expanding the arguments of a function call was introduced in
    Twig 3.15.

* ``=>``: The arrow operator allows the creation of functions. A function is
  made of arguments (use parentheses for multiple arguments) and an arrow
  (``=>``) followed by an expression to execute. The expression has access to
  all passed arguments. Arrow functions are supported as arguments for filters,
  functions, tests, macros, and method calls.

  For instance, the built-in ``map``, ``reduce``, ``sort``, ``filter``, and
  ``find`` filters accept arrow functions as arguments:

  .. code-block:: twig

      {{ people|map(p => p.first_name)|join(', ') }}

  Arrow functions can be stored in variables:

  .. code-block:: twig

      {% set first_name_fn = (p) => p.first_name %}

      {{ people|map(first_name_fn)|join(', ') }}

  .. versionadded:: 3.15

    Arrow function support for functions, macros, and method calls was added in
    Twig 3.15 (filters and tests were already supported).

  Arrow functions can be called using the :doc:`invoke </filters/invoke>`
  filter.

  .. versionadded:: 3.19

    The ``invoke`` filter has been added in Twig 3.19.

Operators
~~~~~~~~~

Twig uses operators to perform various operations within templates.
Understanding the precedence of these operators is crucial for writing correct
and efficient Twig templates.

The operator precedence rules are as follows, with the lowest-precedence
operators listed first:

=============================  =================================== =====================================================
Operator                       Score of precedence                 Description
=============================  =================================== =====================================================
``?:``                         0                                   Ternary operator, conditional statement
``or``                         10                                  Logical OR operation between two boolean expressions
``xor``                        12                                  Logical XOR operation between two boolean expressions
``and``                        15                                  Logical AND operation between two boolean expressions
``b-or``                       16                                  Bitwise OR operation on integers
``b-xor``                      17                                  Bitwise XOR operation on integers
``b-and``                      18                                  Bitwise AND operation on integers
``==``, ``!=``, ``<=>``,       20                                  Comparison operators
``<``, ``>``, ``>=``,
``<=``, ``not in``, ``in``,
``matches``, ``starts with``,
``ends with``, ``has some``,
``has every``
``..``                         25                                  Range of values
``+``, ``-``                   30                                  Addition and subtraction on numbers
``~``                          40                                  String concatenation
``not``                        50                                  Negates a statement
``*``, ``/``, ``//``, ``%``    60                                  Arithmetic operations on numbers
``is``, ``is not``             100                                 Tests
``**``                         200                                 Raises a number to the power of another
``??``                         300                                 Default value when a variable is null
``+``, ``-``                   500                                 Unary operations on numbers
``|``,``[]``,``.``             -                                   Filters, sequence, mapping, and attribute access
=============================  =================================== =====================================================

Without using any parentheses, the operator precedence rules are used to
determine how to convert the code to PHP:

.. code-block:: twig

    {{ 6 b-and 2 or 6 b-and 16 }}

    {# it is converted to the following PHP code: (6 & 2) || (6 & 16) #}

Change the default precedence by explicitly grouping expressions with
parentheses:

.. code-block:: twig

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

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

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

.. _templates-whitespace-control:

Whitespace Control
------------------

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:

.. code-block:: html+twig

    {% 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>' #}

Extensions
----------

Twig can be extended. If you want to create your own extensions, read the
:ref:`Creating an Extension <creating_extensions>` chapter.

.. _`Twig bundle`:                          https://github.com/uhnomoli/PHP-Twig.tmbundle
.. _`vim-twig plugin`:                      https://github.com/lumiliet/vim-twig
.. _`Twig plugin`:                          https://github.com/pulse00/Twig-Eclipse-Plugin
.. _`Twig language definition`:             https://github.com/gabrielcorpse/gedit-twig-template-language
.. _`Twig syntax mode`:                     https://github.com/bobthecow/Twig-HTML.mode
.. _`other Twig syntax mode`:               https://github.com/muxx/Twig-HTML.mode
.. _`Notepad++ Twig Highlighter`:           https://github.com/Banane9/notepadplusplus-twig
.. _`web-mode.el`:                          https://web-mode.org/
.. _`regular expressions`:                  https://www.php.net/manual/en/pcre.pattern.php
.. _`PHP-twig for atom`:                    https://github.com/reesef/php-twig
.. _`TwigQI`:                               https://github.com/alisqi/TwigQI
.. _`TwigStan`:                             https://github.com/twigstan/twigstan
.. _`Twig pack`:                            https://marketplace.visualstudio.com/items?itemName=bajdzis.vscode-twig-pack
.. _`Modern Twig`:                          https://marketplace.visualstudio.com/items?itemName=Stanislav.vscode-twig
.. _`Twig Language Server`:                 https://github.com/kaermorchen/twig-language-server/tree/master/packages/language-server
.. _`Twiggy`:                               https://marketplace.visualstudio.com/items?itemName=moetelo.twiggy
.. _`PHP spaceship operator documentation`: https://www.php.net/manual/en/language.operators.comparison.php