How to give MIME type in XML format?

Question

MIME types

wrote a gateway for processing a qiwi wallet, there was an incomprehensible error. contacted qiwi technical support, to which they answered
Wrong MIME type is being sent: expect "text/xml", get "text/html":
[2015.12.23 12:04:51,514] [INFO] [RMI TCP Connection(829253 )-10.12.42.121] [s1548] app_version=1.105.0; counter=005238350000000044; message=
---- XML ​​request: ----
POST /qiwi HTTP/1.1
Content-type: application/x-www-form-urlencoded
User-Agent: QWClient 1.0 (Java)
Accept: text/xml
Authorization:Basic Mj ***VhhNDlO
command=bill&bill_id=_TEST_1&status=paid&error=0&amount=100.00&user=tel%3A%2B0&prv_name=235319&ccy=RUB&comment=%D1%8B%D1%84%D0%B2
---- XML ​​response: ----
HTTP/1.
Vary: Accept-Encoding
Date: Wed, 23 Dec 2015 09:04:51 GMT
Content-Length: 169
Connection: keep-alive
Content-Type: text/html
Server: nginx
Parse error : syntax error, unexpected T_EXIT in /home/ users/f/fastcomputers/domain
---- Events: ----
2015.12.23 12:04:51:490: Starting test notification for merchantProviderId=235319, [email protected]
2015.12 .23 12:04:51:492: Notification process for bill 0 (prv_id = 235319, trm_txn_id = _TEST_1) started
2015.12.23 12:04:51:493: Connection establishing
2015.12.23 12:04:51:494: Sending notification data
2015.12.23 12:04:51:497: Notification data has been sent. Reading...
2015.12.23 12:04:51:510: Wrong content
type : 'text/html' expected 'text/xml'; actual 'text/html'
tell me what to do?!