code: public function getStates(): array
      {
          static $states;
  
          if (null === $states) {
              $states = [];
              $class = new ReflectionClass($this);
  
              foreach ($class->getConstants() as $constant => $value) {
                  if ('STATE_' === substr($constant, 0, 6)) {
                      $states[] = $value;
                  }
              }
          }
  
          return $states;
      }
docs: Get states
  
  @return array