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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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5
whatuwant
6 months 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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