New in Symfony 5.4: PHP Enumerations Support

PHP Enumerations, or „PHP enums“ for short, is one of the most anticipated
new features of PHP 8.1 (released on November 25, 2021). Their most common use
case is to group several related values. In previous PHP versions you had to
define a series of related constants to achieve that. In PHP 8.1 you can do this:

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// Defining the enumeration and its values
namespace AppConfig;

enum TextAlign
{
case Left;
case Center;
case Right;
}

// Using the enumeration as a data type
use AppConfigTextAlign;

class SomeClass
{
public function setTextAlignment(TextAlign $alignment)
{
// …
}
}

// Using the enum in action
$someObject->setTextAlignment(TextAlign::Center);

PHP Enumerations are modeled as ADT (Algebraic Data Type) values, so they can
define methods, implement interfaces, define values, etc. In Symfony 5.4 we’ve
added support for PHP enums in different components.

PHP Enums Support in Symfony Forms

Contributed by
Alexander M. Turek
in #43095.

The Form component has added a new EnumType field so you can represent
PHP enums as a selection of values. Consider this example:

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enum Suit: string
{
case Hearts = ‚H‘;
case Diamonds = ‚D‘;
case Clubs = ‚C‘;
case Spades = ‚S‘;
}

enum Rank: string
{
case Ace = ‚A‘;
case King = ‚K‘;
case Queen = ‚Q‘;
case Jack = ‚J‘;
case Ten = ‚X‘;
case Nine = ‚9‘;
case Eight = ‚8‘;
case Seven = ‚7‘;
case Six = ‚6‘;
case Five = ‚5‘;
case Four = ‚4‘;
case Three = ‚3‘;
case Two = ‚2‘;
}

final class Card
{
public ?Suit $suit = null;
public ?Rank $rank = null;
}

Use the new EnumType class to represent these PHP enums as form fields:

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// src/Form/Type/CardType.php
namespace AppFormType;

use AppConfigSuit;
use AppConfigRank;
use SymfonyComponentFormAbstractType;
use SymfonyComponentFormExtensionCoreTypeEnumType;
use SymfonyComponentFormExtensionCoreTypeSubmitType;
use SymfonyComponentFormFormBuilderInterface;

class CardType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options): void
{
$builder
->add(’suit‘, EnumType::class, [‚class‘ => Suit::class, ‚expanded‘ => true])
->add(‚rank‘, EnumType::class, [‚class‘ => Rank::class])
->add(’submit‘, SubmitType::class)
;
}

// …
}

This is how the form will look like in Symfony 5.4:

PHP Enums Support in Symfony Serializer

Contributed by
Alexandre Daubois
in #40830.

PHP enums that define scalar values for their entries are called „backed enums“.
When properties use that kind of PHP enum, the Symfony Serializer component
can normalize and denormalize those properties:

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final class Card {
public Suit $suit;
}

$card = new Card();
$card->suit = Suit::Diamonds;
$serialized = $this->serializer->serialize($card, ‚json‘)
// expected: ‚{ „suit“: „D“ }‘

$this->serializer->deserialize($serialized, Card::class);
// expected: Card->suit === Suit::Diamonds

PHP Enums Support in other components

Alexandre Daubois also contributed other Pull Requests to add PHP enums
support in other Symfony components:

Pull Request #40857
added enums support when dumping the Dependency Injection container;
Pull Request #41072
added enums support to VarExporter component.

PHP Enumerations are fantastic and Symfony 5.4 will fully support them since day one.

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