Getting an PHP enum from dynamic name

Question

I´m trying to create an php 8.1 enum from a dynamic name. Seems not to be possible. So given an enum

enum Foo {
    case bar;
}

The following works of course: Foo::bar While this doesn´t:

$name = "bar";
Foo::${$name}

This results in: Access to undeclared static property App\Console\Commands\Foo::$bar

I tried various tricks here, to no avail. It seems not to be possible to get an enum instance from a dynamic name. My custom and quick workaround looks like this, a static factory:

/**
 * @throws \Exception
 */
public static function fromName(string $name) : self {

    foreach(Foo::cases() as $enum){
        if($enum->name === $name){
            return $enum;
        }
    }
    throw new \Exception("Not a valid enum name");
}

I could put this in a trait and inherit this in all my enums, yes, problem solved.

My question is: am I missing something here? Is it really not possible to instantiate an enum with native php methods? Or am I thinking in the wrong direction?

The pre php8.1 class-as-enum composer packages used to have those convenience methods, see https://github.com/bensampo/laravel-enum So why is this pretty common case not part of the specification (just curious)?

Answer 1

The most simple way for that is using the constant() function:

<?php namespace App\Enums;


enum FooEnum: int
{
    case FOO = 123;
    case BAR = 456;
   
    public static function fromName(string $name){
        
        return constant("self::$name");
    }
}

Usage:

$name = "FOO";
dump(App\Enums\FooEnum::fromName($name));

/*
return 
App\Enums\FooEnum {
  +name: "FOO"
  +value: 123
}
*/

Answer 2

PHP 8.3+

Following syntax is supported since PHP 8.3:

<?php

$enumName = 'Something';
SomeEnum::{$enumName};
SomeEnum::{$enumName}->value;

This works for both constants and enum cases. It was basically done for constants as "dynamic class constant fetch": https://www.php.net/releases/8.3/en.php#dynamic_class_constant_fetch as since enums are basically implemented as a special case of class with special contants (cases) - it works for them too.

PHP 8.1 & 8.2

You can use constant() as you would use for a constant, but be aware of namespaces! by the way this is the same issue as with defined & const definition - even when inside the namespace, you have to specify it in the reference string!

Namespace example

namespace SomeNamespace;
enum MyEnum: int {
    case SomeName = 42;
}

$name ='SomeName';
echo constant("SomeNamespace\MyEnum::$name")->value;

Simple example (without namespace)

enum MyEnum: int {
    case SomeName = 42;
}

$name ='SomeName';
echo constant("\MyEnum::$name")->value;