Enum case as Array key?

[geraldofebrian]

Description

Before enum exist, i used constant to define the array key. Now i want to use enum. But i got error when i declare the enum as array key. so i do the workaround like this:

if (!function_exists('_api')) {
    /**
     * use enum as Array Key.
     *
     * @param array $values
     * @param \App\Enums\Api\ResponseKey $key
     * @param mixed $data
     * @return array
     */
    function _api(?array &$values, ResponseKey $key, $data)
    {
        if (! is_array($values)) $values = [];

        $values[$key->value] = $data;

        return $values;
    }
}

Then call it like _api($data, ResponseKey::message, "success");

Can this workaround can be implemented as feature for future PHP?

[iluuu1994]

There's an RFC for this: https://wiki.php.net/rfc/object_keys_in_arrays AFAIK the author has no interest in pursuing this RFC any further but somebody else might do so in the future. Another option you have for now is using SplObjectStorage or WeakMap instead of arrays.

[mvorisek]

On of the major problem with the RFC objects as keys is #6588 (comment). Given enums are unique by definition, this feature request makes sense even if objects as keys in general are not supported.

[daftspunk]

A nice casting interface is probably all that is needed here.

// Casts to scalar
$array[StatusEnum::DRAFT] 

// Casts back to enum
(StatusEnum) 'draft'

The same can be applied to all objects, like what we find in C#.

// Cast array to a custom object
$collection = (MyCollection) $array

With some __method to handle incoming and outgoing logic.

// In
public static function __castStatic(mixed $from): mixed
{
    return new static($from);
}

// Out
public function __toCasted(): mixed
{
    return $this->toArray();
}

[SuitespaceDev]

Honestly; I cannot fathom why

$team[ role::lead ] = $some_person;

does not automatically assume role::lead->value.

Traditionally enums are used to get associative benefits with indexed arrays, as well as providing bitwise combinations in function arguments and working as a constraint system.

There are three things PHP is constantly lacking and constantly avoiding taking on

• True overload system (operator overloads and real function signature overloads)
• Object keys
• Entity-to-Entity Type casting (or even just better magic methods)

Any of these three singularly solve a large swathe of use cases. There are so many concepts in other languages that would fit great in PHP if only one of these existed. Any one of these makes the other 2 much easier to implement as well.

Once again this is true for efficient enum usage.
As presently implemented, enums are practically fighting their own existence.
(ie, I can target ->name and a string backed value separately, but not actually use enums as typesafe labels on values)

All this said, if the interpreter just assumes ->value instead of erroring, like any reasonable enum implementation should -- as enums have the job of being a countable label, then you could indeed meet the bare minimum of needs for enums across a decent number of use cases.

[hguenot]

SplObjectStorage (and ArrayAccess) cannot be used with array_key_exists (and maybe some other array_*** functions).
I think it would be very usefull and easier to use Enum as array key. Also it will reduce the impact of moving from const class attributes to enum...

[ahajzik-crido]

I'm also very interested in enums as array keys. It's something obvious in other mature programming languages. I miss it as I could use it before. I thought it would be added in PHP 8.3, but I don't see such proposal.
Please consider this as an important request. Enums are not just objects, they are UNIQUE cases and it is natural to use them as index (not their internal values).

[oplanre]

For anyone still stuck on this, check out the php-ds extension which provides some nice data structures to help with this

[TheApproach]

Noted data-structures in php-ds do not appear to have native enums or cases as array keys

Is there some update which completed this?