PHP: Hypertext Preprocessor

枚举常量

虽然 enum 可以包括 public、private、protected 的常量，但由于它不支持继承，因此在实践中 private 和 protected 效果是相同的。

枚举常量可以引用枚举条目：

<?php

enum Size
{
    case Small;
    case Medium;
    case Large;

    public const Huge = self::Large;
}
?>

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Hayley Watson ¶

1 year ago

Just to clarify, enum constants *can* contain cases, but they don't *have* to; other constant values are legitimate - including cases of other Enumerations.

<?php
enum Suit
{
    case Hearts;
    case Clubs;
    case Spades;
    case Diamonds;

    public const Card = Size::Large; // A case from a different enum
}

enum Size
{
    case Small;
    case Medium;
    case Large;

    public const Scale = 297/210; // A float
}

echo Suit::Diamonds::Card::Scale; // Getting the constant Scale from the constant Card in a Suit.
?>