code: public function build() {
          $built = array();
          if ($this->fieldname) {
              $built[$this->fieldname] = array();
              foreach (array("from","to","includeLower","includeUpper", "boost") as $opt) {
                  if ($this->$opt !== null)
                      $built[$this->fieldname][$opt] = $this->$opt;
              }
              if (count($built[$this->fieldname]) == 0)
                  throw new \ElasticSearch\Exception("Empty RangeQuery cant be created");
          }
          return $built;
      }
docs: Build to array
  
  @throws \ElasticSearch\Exception
  @return array