Unbacked Enum

Unbacked enums are enumeration without a string or integer equivalent for each of its cases.

Unbacked enums are the default cases, and are implied when not mentioned. The opposite is backed enum.

<?php

enum Ecclectic {
    case PHP;
    case ELEPHPANT;
    case SYNTAX_ERROR;
    case SPADE;
}

?>

Documentation

Related : Enumeration (enum), Backed Enum, BackedEnum

Added in PHP 8.1