Enums PoC

gistfile1.php

<?php
namespace Derp;

abstract class Enum
{
    protected $value;

    protected static $possibleValues;

    protected static function getPossibleValues()
    {
        if (static::$possibleValues) {
            return static::$possibleValues;
        }

        $reflectionClass = new \ReflectionClass(get_called_class());
        static::$possibleValues = $reflectionClass->getConstants();

        return static::$possibleValues;
    }

    /**
     * @param $name
     * @param $arguments
     * @return static
     * @throws \Exception
     */
    public static function __callStatic($name, $arguments)
    {
        $possibleValues = static::getPossibleValues();
        if (!array_key_exists($name, $possibleValues)) {
            throw new \Exception;
        }

        if (count($arguments) > 0) {
            throw new \Exception;
        }

        return self::createInstance($name, $possibleValues[$name]);
    }

    /**
     * @param $value
     * @return static
     */
    protected static function createInstance($value)
    {
        $enum = new static;
        $enum->value = $value;
        return $enum;
    }

    protected function getValue()
    {
        return $this->value;
    }

    public function equals(Enum $otherValue)
    {
        return get_class($otherValue) === get_called_class() && $otherValue->getValue() === $this->getValue();
    }

    public static function all()
    {
        return array_map(
            function($value) {
                return static::createInstance($value);
            },
            static::getPossibleValues()
        );
    }
}


class Day extends Enum
{
    const MONDAY = 'monday';

    const FRIDAY = 'friday';
}

$monday = Day::MONDAY();

var_dump($monday->equals(Day::FRIDAY()));
var_dump(Day::all());