i have two input field, the first have autocomplete with cities names, I need to set the second field zone, with autocomplete filtered by selected city... i tried this but dont work...

$("#zone").focus(function(){ 
        var c = $('#city').val();
          $('#zone').autocomplete({
            source: '/auto_q_int.php?city=' + c
                                 });
                             });

auto_q_int.php is:

    class Autocomplete
{
    public $term;
    public $conn;

        public function __construct()
        {
            $this->dbConnect();
            $this->term = mysql_real_escape_string($_GET['term']);

        }

        private function dbConnect()
        {
            $this->conn = mysql_connect(HOST,USER,PASSWORD) OR die("connection failed");
            mysql_select_db(DB, $this->conn) OR die("no db selected");
        }

        public function printResult()
        {
            $sql = "SELECT zone
            FROM zones
            WHERE zone LIKE '%$this->term%' && id = '$_GET[city]'
            ORDER BY zone ASC";

            $res = mysql_query($sql, $this->conn);

            $return = array();
            $arr = array();

            while($row = mysql_fetch_array($res))
            {
                array_push($return, $arr);
            }

            echo json_encode($return);
        }
}

$autocomplete = new Autocomplete();
$autocomplete->printResult();

some help please?