question about PDO and formatting output

I have the following code:

$db = Frapi_Database::getInstance();
         $origin = $this->getParam('origin', self::TYPE_STRING);
         $destination = $this->getParam('destination', self::TYPE_STRING);
            $stmt = $db->prepare("SELECT DEPARTURE_TIME, TIME FROM TRAVELTIME WHERE ORIGIN = ? AND DESTINATION = ?");
            $stmt->execute(array($origin, $destination));
            //$time = $stmt->fetchColumn();
         $this->data = $stmt->fetchAll(PDO::FETCH_ASSOC);
         var_dump($this->data);

This however gives me something like:

array(30) {
  [0]=>
  array(2) {
    ["DEPARTURE_TIME"]=>
    string(5) "12:00"
    ["TIME"]=开发者_如何学JAVA>
    string(2) "99"
  }
  [1]=>
  array(2) {
    ["DEPARTURE_TIME"]=>
    string(5) "12:15"
    ["TIME"]=>
    string(3) "105"
  }
  [2]=>
  array(2) {
    ["DEPARTURE_TIME"]=>
    string(5) "12:30"
    ["TIME"]=>
    string(3) "115"
  }
  [3]=>
  array(2) {
    ["DEPARTURE_TIME"]=>
    string(5) "12:45"
    ["TIME"]=>
    string(3) "122"
  }

}

I don't want this to be like this format, I want it to be:

{"DEPARTURE_TIME":"12:00","TIME":"99"}, {"DEPARTURE_TIME":"12:15","TIME":"123"} and so on

I did a json_decode and I got:

{"DEPARTURE_TIME":"12:00","0":"12:00","TIME":"99","1":"99"},{"DEPARTURE_TIME":"12:15","0":"12:15","TIME":"105","1":"105"}

don't know why this is

For this case

print implode(', ', array_map(function($a){
    print '{"DEPARTURE_TIME":"'.$a["DEPARTURE_TIME"].'","TIME":"'.$a['TIME'].'"}';
}));

For all cases you can use json_encode

$this->data = $stmt->fetchAll(PDO::FETCH_OBJ); // as I check it's ok to use PDO_FETCH_ASSOC too
json_encode($this->data);