Enum

Enum.php

<?php

abstract class Enum extends \ArrayObject
{
    public final function __construct()
    {
        $constantsToRemove = ['STD_PROP_LIST', 'ARRAY_AS_PROPS'];
        $constants         = (new \ReflectionObject($this))->getConstants();

        foreach ($constants as $constant => $value) {
            if (!in_array($constant, $constantsToRemove)) {
                $this[$constant] = $value;
            }
        }
    }
}

index.php

<?php

$ua = new UserActions;

var_dump($ua->getArrayCopy());

foreach ($ua as $constant => $value) {
    echo sprintf('Constant "%s", Value "%s"', $constant, $value).PHP_EOL;
}

UserActions.php

<?php

class UserActions extends Enum
{
    const UPDATED = 'user.updated';
    const CREATED = 'user.created';
}