code: public static function toArray() : array
      {
          if (static::$array == null) {
              $ref = new \ReflectionClass(static::class);
              $consts = $ref->getConstants();
              static::$array = array();
              foreach ($consts as $key => $value) {
                  if (stripos($key, 'VALUE_') === 0) {
                      static::$array[$key] = $value;
                  }
              }
          }
  
          return static::$array;
      }
docs: Return keys and values as an associative array.
  
  @return array