# Enumerations & BitSets¶

• Use an enumeration if you have a fixed list of values.
• Use a bitset if you have a list of boolean flags.

Do not use PHP constants directly if your code is meant to be extendable, as constants cannot be deprecated, but the values of an enumeration or methods of a BitSet can.

## Background and history¶

PHP has no enumeration concept as part of the language up to date. Therefore the TYPO3 Core includes a custom enumeration implementation.

In TYPO3 enumerations are implemented by extending the abstract class TYPO3\CMS\Core\Type\Enumeration. It was originally implemented similar to SplEnum which is unfortunately part of the unmaintained package PECL spl_types.

It was proposed to include an enumeration concept in future versions of PHP (see Enumeration proposal in PHP) this might make it possible to drop the concept from the Core.