boundaries.enum.php

<?php

enum Boundaries
{
    case INCLUDE_NONE(false, false);
    case INCLUDE_START(true, false);
    case INCLUDE_END(false, true);
    case INCLUDE_ALL(true, true);

    protected bool $startIncluded;
    protected bool $endIncluded;

    private function __construct($startIncluded, $endIncluded)
    {
         $this->startIncluded = $startIncluded;
         $this->endIncluded = $endIncluded;
    }

    public function startIncluded(): bool
    {
         return $this->startIncluded;
    }

    public function endIncluded(): bool
    {
         return $this->endIncluded;
    }
}

Example based on this blog post: https://stitcher.io/blog/enums-without-enums