ServerUnsupported content type: application/x-www-form-urlencoded

Merhabalar,

$username = 'demo';
$password = '123456';
$xml_data = '<prod:deleteProduct>'.
' <apiKey>demo87</apiKey>'.
' <sign>demo65</sign>'.
' <time>'.date("Y-m-d H:i:s").'</time>'.
' <productIdList>'.
' <item>539087067</item>'.
' </productIdList>'.
' <itemIdList>'.
' </itemIdList>'.
' <lang>tr</lang>'.
'</prod:deleteProduct>';


$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,'https://demo.com/demo');
curl_setopt($ch, CURLOPT_USERPWD, "$username:$password");
curl_setopt($ch,CURLOPT_POST,true);

curl_setopt($ch,CURLOPT_POSTFIELDS,$xml_data);
curl_exec($ch);
curl_close($ch);

Almış olduğum hata ServerUnsupported content type: application/x-www-form-urlencoded nasıl çözebilirim