时间戳无法进入Mysql

This time I had a problem in Mysql with message error :

2016-10-11 16:16:15
object(DateTime)#1 (3) { ["date"]=> string(26) "2016-10-11 16:16:15.000000" ["timezone_type"]=> int(3) ["timezone"]=> string(12) "Asia/Jakarta" }

Catchable fatal error: Object of class DateTime could not be converted to string in /opt/lampp/htdocs/bus/index.php on line 16

I want the data to $d can get into mysql and the results of the timestamp can get into mysql without error.

And this is source code try:

$d = new DateTime('2016-10-11T09:16:15.000Z');$d->setTimezone(new DateTimeZone('Asia/Jakarta'));
echo $d->format('Y-m-d H:i:s')."<br />"; // 2016-10-06T09:50:54.000000
var_dump($d);


$host="localhost";
$user="root";
$pass="";
$db="baru";

/*Koneksi database*/
 $spot = mysql_connect($host, $user, $pass) or die ("Koneksi gagal");
 mysql_select_db($db, $spot) or die ("Koneksi gagal");

$sql = "INSERT INTO time (`timestamp`) values ( '$d' )"; 
mysql_query($sql);

with structure DB:

______ Name ________ Type _____________ Collation ______
1   id(Primary)     int(40)             
2   timestamp       varchar(30)     latin1_swedish_ci

Thanks.