New in Twig 3.15 (part 2)

Dot Operator Improvements

Contributed by Fabien Potencier in #4310

The attribute() function allows accessing attributes or properties of variables or objects where the name of the attribute/property is dynamic:

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{# the dot notation can be used because the property name ('fullName') is known and static #}
{{ user.fullName }}

{# attribute() is needed because the name of the property is stored in a variable #}
{% for property in ['fullName', 'email', 'phoneNumber'] %}
    {{ attribute(user, property) }} <br>
{% endfor %}

In Twig 3.15, the attribute() function is deprecated, and the dot operator has been extended to handle dynamic properties:

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{# wrap dynamic properties with parentheses #}
{% for property in ['fullName', 'email', 'phoneNumber'] %}
    {{ user.(property) }} <br>
{% endfor %}

Although the attribute() is deprecated, it will remain available in Twig 4.0 to ensure a smoother upgrade path.

Contributed by Nicolas Grekas in #4353

Another enhancement to the dot operator is the ability to access class constants directly from an object:

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{# previously, you needed to pass the fully qualified class name #}
{{ constant('App\\Some\\Namespace\\Of\\Some\\Class::CONSTANT_NAME') }}

{# now, you can also use any object of the class containing the constants #}
{# SHIPPING_TYPE_EXPEDITED is the name of a constant in the Order class #}
{{ order.SHIPPING_TYPE_EXPEDITED }}

Named Arguments Improvements

Contributed by Fabien Potencier in #4391

Twig macros are similar to functions in programming languages and they are useful to reuse template fragments. Starting from Twig 3.15, you can use named arguments when calling a macro, with the syntax argument: value, just like in PHP:

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{{ forms.field(type: 'text', name: 'user[name]') }}

Named arguments are also supported when passing arguments with the dot operator:

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{{ user.fullName(maxLength: 32) }}

{% for property in ['fullName', 'email', 'phoneNumber'] %}
    {{ user.(property)(escape: true, maxLength: 32) }} <br>
{% endfor %}

With these changes, named arguments are now supported everywhere: functions, filters, tests, macros, and dot operator arguments.

Free-Form PHP Callable Argument Names

Contributed by Fabien Potencier in #4318

Previously, Twig required snake_case argument names when calling PHP callables, regardless of their original signature. In Twig 3.15, you can use either snake_case or camelCase, no matter which format is used by the PHP signature:

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{# both syntaxes yield the same result #}
{{ order.summary(include_total: true) }}
{{ order.summary(includeTotal: true) }}

Argument Unpacking

Contributed by Fabien Potencier in #4300

The ... spread operator can now expand arguments when calling a function:

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{% set attr = [{type: 'submit'}, {class: 'btn btn-primary'}, {'data-tracking-id', '12345'}] %}
{{ html_attributes(...attr) }}

Arrow Functions in All Twig Callables

Contributed by Fabien Potencier in #4378

Arrow functions, a favorite of many developers, are now supported everywhere in Twig. Previously supported in filters and functions, they can now also be used in tests, macro arguments, and method call arguments:

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{% set people = [
    {first: "Bob", last: "Smith"},
    {first: "Alice", last: "Dupond"},
] %}

{# passing an arrow function to a macro #}
{{ _self.display_people_names(people, (person) => person.first) }}

Arrow functions can now also be stored in Twig variables:

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{# defining the arrow function and storing it in a variable #}
{% set first_name_fn = (p) => p.first %}

{{ _self.display_people_names(people, first_name_fn) }}