Posting data using Curl in XML Format

Currently post my data in HTTP Post format and i need to post it in XML and add the header.

This is how i currently post my data.

//extract data from the post
extract($_POST);

//set POST variables
$url = 'http://ift.tt/1CVhKw5';
$fields = array(
                        'surname' => urlencode($surname),
                        'first_name' => urlencode($first_name),
                        'dob' => urlencode($dob),
                        'email' => urlencode($email),
                        'home_phone' => urlencode($home_phone),
                        'mobile_phone' => urlencode($mobile_phone),
                        'work_phone' => urlencode($work_phone),
                        'postcode' => urlencode($postcode),
                        'leadid' => urlencode(123),
                        'affid' => urlencode(123),
                        'subid' => urlencode(123),
                        'bank_acno' => urlencode($bank_acno),
                        'bank_sort' => urlencode($bank_sort),
                        'amount_required' => urlencode($amount_required),

                );

//url-ify the data for the POST
foreach($fields as $key=>$value) { $fields_string .= $key.'='.$value.'&'; }
rtrim($fields_string, '&');

//open connection
$ch = curl_init();

//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_URL, $url);
curl_setopt($ch,CURLOPT_POST, count($fields));
curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);

//execute post
$result = curl_exec($ch);

//close connection
curl_close($ch);

How do i post this in XML Format and add a Header : http://www.header.com