enum

Small lightweight library to create enum in PHP without SPLEnum and strict comparisons allowed.

dislcaimer

For project that are build on PHP >=8.1 please use the language build in Enums described in this rfc: https://wiki.php.net/rfc/enumerations This library should not be needed anymore and will not support PHP >8.1.

installation

composer require patchlevel/enum

declaration

First of all you have to define your enum. To do this, you have to inherit from the Enum class, create a few constants (the value must be unique and a string) and define methods that return an enum representation. Here is an example:

<?php

declare(strict_types=1);

namespace Patchlevel\Enum\Example;

use Patchlevel\Enum\Enum;

/**
 * @psalm-immutable
 */
final class Status extends Enum
{
    private const CREATED = 'created';
    private const PENDING = 'pending';
    private const RUNNING = 'running';
    private const COMPLETED = 'completed';

    public static function created(): self
    {
        return self::get(self::CREATED);
    }

    public static function pending(): self
    {
        return self::get(self::PENDING);
    }

    public static function running(): self
    {
        return self::get(self::RUNNING);
    }

    public static function completed(): self
    {
        return self::get(self::COMPLETED);
    }
}

self::get() ensures that exactly one instance of a representation really exists so that strict comparisons can be used without problems.

Alternatively, you can inherit the ExtendedEnum, which comes with a few conveniences, more about this under ExtendedEnum.

api

work with enum

<?php 

declare(strict_types=1);

namespace Patchlevel\Enum\Example;

$status = Status::completed();

if ($status === Status::completed()) {
    echo "That's working";
}

// or use as typehint

function isFinished(Status $status): bool {
    return $status === Status::completed();
}

echo isFinished($status) ? 'yes' : 'no'; 

// or with the new php8.0 match feature:

$message = match ($status) {
    Status::created() => 'Process created',
    Status::pending() => 'Process pending',
    Status::running() => 'Process running',
    Status::completed() => 'Process completed',
    default => 'unknown status',
};

echo $message; // Process completed

Strict comparisons are not a problem as it ensures that there is only one instance of a certain value.

fromString

You can create an enum from a string. It is checked internally whether the value is valid, otherwise an InvalidValue exception is thrown.

$status = Status::fromString('pending');

if ($status === Status::pending()) {
    echo 'it works';
}

toString

The other way around, an enum can also be converted back into a string.

$status::completed();
echo $status->toString(); // completed

equals

The Equals method is just a wrapper for $a === $b.

$status = Status::completed();
$status->equals(Status::pending()); // false

isValid

isValid can be used to check whether the transferred value is valid. The return value is a boolean.

Status::isValid('foo'); // false
Status::isValid('completed'); // true

values

You can also get all Enum instances.

$instances = Status::values();

foreach ($instances as $instance) {
    echo $instance->toString(); // completed, pending, ...
}

keys

Or all keys.

$keys = Status::keys();

foreach ($keys as $key) {
    echo $key; // completed, pending, ...
}

extended enum

Alternatively, it can also extend from ExtendedEnum. This implementation also provides other features mostly magic methods: __toString, __callStatic and implementing \JsonSerializable.

<?php

declare(strict_types=1);

namespace Patchlevel\Enum\Example;

use Patchlevel\Enum\ExtendedEnum;

/**
 * @psalm-immutable
 * @method static self CREATED()
 * @method static self PENDING()
 * @method static self RUNNING()
 * @method static self COMPLETED()
 */
final class Status extends ExtendedEnum
{
    private const CREATED = 'created';
    private const PENDING = 'pending';
    private const RUNNING = 'running';
    private const COMPLETED = 'completed';
}

__callStatic

With the magic method __callStatic it is possible to create an Enum instance based only on the constant names. So no extra method is needed to be defined. If the constant name doesn't exist in the enum a BadMethodCall exception is thrown.

$status = Status::CREATED();

__toString

Just the magic method implementation of toString.

$status = Status::CREATED();
echo (string)$status; // created

JsonSerializable

The ExtendedEnum already implements the method jsonSerialize from the interface \JsonSerializable. This means that \json_encode will automatically serialize the value in the right manner. Beware that \json_decode won't automatically decode it back into the enum. This job must be tackled manually. See this example:

$status = Status::CREATED();
echo json_encode($status, JSON_THROW_ON_ERROR); // "created"