PHP Enums

Devls_Enum.php

<?php

/**
 * Enum Abstract Class
 *
 * Warning: Uses Reflection and LSB. :D
 * ==========================================================
 *
 * To use this class:
 *
 * Create a concrete implementation, and define class constants.
 *
 * ==========================================================
 *
 * To validate call ConcreteEnum::isValid( 'SOME_ENUM_VAL' )
 *
 * This will return a boolean response
 *
 * === OR ===================================================
 *
 * new ConcreteEnum( 'SOME_ENUM_VAL' )
 *
 * The second version will throw an exception
 *
 * ==========================================================
 */

namespace {
    abstract class Devls_Enum {

        /* @var string[][] */
        private static $constants = [];

        /* @var string */
        private $value;

        /* @var string */
        protected $default = false;

        /**
         * @param [string $value]
         * @throws \UnexpectedValueException
         */
        final public function __construct( $value = null )
        {
            if( ! static::isValid( $value )
                || ( $value === null && $this->default === false ) ) {
                $this->throwUnexpectedValueException();
            } elseif ( $value === null
                       && $this->default !== false ) {
                $this->value = (string)$this->default;
            } else {
                $this->value = (string)$value;
            }
        }

        /**
         * Override this to change the exception thrown.
         *
         * @throws \Exception
         */
        protected function throwUnexpectedValueException()
        {
            throw new UnexpectedValueException;
        }

        /**
         * @return string
         */
        final public function __toString()
        {
            return $this->value;
        }

        /**
         * @return string
         */
        final public function __invoke()
        {
            return $this->value;
        }

        /**
         * @return string
         */
        final public function getValue()
        {
            return $this->value;
        }

        /**
         * @return string[]
         */
        final public static function getEnumerations()
        {
            $class = get_called_class();

            if( isset( self::$constants[$class] ) ) {
                return self::$constants[$class];
            }

            $reflect = new ReflectionClass($class);
            return self::$constants[$class] = $reflect->getConstants();
        }

        /**
         * @param string[] $enumerations
         * @param [string $default]
         * @return \Devls_Enum_Dynamic
         */
        final public static function defineDynamicEnum( array $enumerations, $default = null )
        {
            $enumName = \Devls\Enum\dodgy_enum_creator();

            $enumerations = array_combine( $enumerations, $enumerations );
            self::$constants[$enumName] = $enumerations;
            return new \Devls_Enum_Dynamic( $enumName, $default === null ? false : $default );
        }

        /**
         * @param $value
         * @return bool
         */
        final public static function isValid( $value )
        {
            return array_key_exists( $value, static::getEnumerations() );
        }

    }
}

namespace Devls\Enum {

    /**
     * @return string
     */
    function dodgy_enum_creator() {
        $name = 'enum'.time().md5(mt_rand(1,100000));
        $php = <<<PHP
class {$name} extends \Devls_Enum {

}
PHP;
        eval ( $php );
        return $name;

    }
}

Devls_Enum_Dynamic.php

<?php
/**
 * More heavy reflection
 */
class Devls_Enum_Dynamic {

    /* @var $string */
    private $name;

    /* @var string */
    private $default;

    public function __construct( $name, $default )
    {
        if( !class_exists( $name ) || !is_subclass_of( $name, 'Devls_Enum' ) ) {
            throw new Exception( 'Invalid use of Devls_Enum_Dynamic' );
        }

        $this->name = $name;
        $this->default = $default;
    }

    /**
     * @param [string $value]
     * @return \Devls_Enum
     */
    public function getInstance( $value = null )
    {
        $reflect = new ReflectionClass( $this->name );
        /* @var $instance \Devls_Enum */
        $instance = $reflect->newInstanceWithoutConstructor();

        $property = $reflect->getProperty( 'default' );
        $property->setAccessible( true );
        $property->setValue( $instance, $this->default );
        $property->setAccessible( false );
        $instance->__construct( $value );

        return $instance;

    }

}