\DB::table("users")
     ->select("users.id", \DB::raw("6371 * acos(cos(radians(" . $this->lat . "))
     * cos(radians(users.latitude)) 
     * cos(radians(users.longitude) - radians(" . $this->lng . ")) 
     + sin(radians(" .$this->lat. ")) 
     * sin(radians(users.latitude))) AS distance"))
     ->having('distance', '<', $this->rad)
     ->first();