Enumeration example of the Object Value Design Pattern

PostStatus.php

<?php

class PostStatus
{
    const PRIVATE = 'private';
    const DRAFT = 'draft';
    const PUBLISHED = 'published';
    const TRASHED = 'trash';

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

    public static function all()
    {
        return [
            self::PRIVATE,
            self::DRAFT,
            self::PUBLISHED,
            self::TRASHED
        ];
    }

    public function __construct($value)
    {
        if (! in_array($value, self::all())) {
            throw new InvalidArgumentException("Invalid PostStatus value: {$value}");
        }

        $this->value = $value;
    }

    public function __toString()
    {
        return $this->value;
    }

    public function is($comparison)
    {
        if ($comparison instanceof self) {
            return $comparison->value === $this->value;
        } else {
            return $comparison === $this->value;
        }
    }
}