The BackedEnum interface

    (PHP 8 >= 8.1.0)

    Introduction

    The BackedEnum interface is automatically applied to backed enumerations by the engine. It may not be implemented by user-defined classes. Enumerations may not override its methods, as default implementations are provided by the engine. It is available only for type checks.

    Interface synopsis

    interface BackedEnum extends UnitEnum {
    /* Methods */
    public static from(int|string $value): static
    public static tryFrom(int|string $value): ?static
    /* Inherited methods */
    public static UnitEnum::cases(): array
    }

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    User Contributed Notes 1 note

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    8
    whatuwant
    2 years ago
    As of PHP 8.1, while `UnitEnum` & `BackedEnum` cannot be implemented by user-defined classes, it seems they can be extended by user-defined interfaces and eventually be implemented by enums.

    <?php

    interface TestEnumInterface extends \BackedEnum
    {
    public function     foo(): string;
    }

    enum TestEnum: string implements TestEnumInterface
    {
    case     CASE_1 = 'case 1';
    case     CASE_2 = 'case 2';

    public function     foo(): string
    {
    return     'bar';
    }
    }

    ?>
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