PHP: Traits - Manual

Traits

Enumerations may leverage traits, which will behave the same as on classes. The caveat is that traits used in an enum must not contain properties. They may only include methods, static methods, and constants. A trait with properties will result in a fatal error.

<?php

interface Colorful
{
    public function color(): string;
}

trait Rectangle
{
    public function shape(): string {
        return "Rectangle";
    }
}

enum Suit implements Colorful
{
    use Rectangle;

    case Hearts;
    case Diamonds;
    case Clubs;
    case Spades;

    public function color(): string
    {
        return match($this) {
            Suit::Hearts, Suit::Diamonds => 'Red',
            Suit::Clubs, Suit::Spades => 'Black',
        };
    }
}
?>

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User Contributed Notes 1 note

down

wervin at mail dot com ¶

1 year ago

One good example of a trait, would be to give a lot of enums a method to retrieve their cases, values or both.

<?php
trait EnumToArray
{
    public static function names(): array
    {
        return array_column(self::cases(), 'name');
        
    }

    public static function values(): array
    {
        return array_column(self::cases(), 'value');
    }

    public static function asArray(): array
    {
        if (empty(self::values())) {
            return self::names();
        }
        
        if (empty(self::names())) {
            return self::values();
        }
        
        return array_column(self::cases(), 'value', 'name');
    }
}
?>

Some example outputs:

<?php
var_export(IpVersion::names());     // ['Ipv4', 'IPv6']
var_export(IpVersion::values());    // []
var_export(IpVersion::asArray());   // ['IPv4', 'IPv6']

var_export(Language::names());      // ['en', 'es']
var_export(Language::values());     // ['English', 'Spanish']
var_export(Language::asArray());    // ['en' => 'English', 'es' => 'Spanish']

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