public function SortURL( $sortby ){
        echo __FILE__ . " on line " . __LINE__ . "<br>";
        $apiQuery = $this->APIQuery();
        if(!empty($apiQuery['sortby']) && $apiQuery['sortby'] == $sortby){
            // change polarity
            $apiQuery['sortdir'] = ($apiQuery['sortdir'] == 'asc')? 'desc' : 'asc';
        }else{
            // change sort + asc
            $apiQuery['sortBy'] = $sortby;
            $apiQuery['sortdir'] = 'asc';
        }
        return "/flight-search?" . http_build_query($apiQuery);
    }