PHP get the date in the XML format

I want to generate the date in XML format from PHP ,

The following is the script that i am looking to generate dynamically:

$voice.trackTransactionPageView({
"orderId" : "55555",
"total" : "40.84",
"userId" : "7448dc2",
"email" : "john@example.com",
"nickname" : "john1981",
"deliveryDate" : "2011-01-21T11:36:47.384",
"locale" : "en_US"
});

if you see in the above code i have the deliveryDate that has the value in xml format so i wanted to generate the same in my code with php.

i have tried with date('Y-m-dTH:i', time());

but it's generating 2014-09-29EDT02:28:11

i am looking to generate 2011-01-21T11:36:47.384.

Please let me know how can i achieve this.

Thanks.