PHP Curl给出错误的请求-无效的标头

1. 当我尝试使用xml头和post字段来处理curl时。我收到错误的请求。我不知道出了什么问题，有人能帮上忙吗？

2. 标头中传递的移动字段数据是经过三重des转换的

$url="www.test.com/api";
$xml = '<?xml version="1.0" encoding="UTF-8"?><a><b>hai</b></a>';
$xml_header = trim('<?xml version="1.0" encoding="UTF-8"?><mobile>4xKReHFU60Ova0aqHxZldg==</mobile>
')  ;
$headers = array(
"Content-type: text/xml",
"Content-length: " .strlen($xml_header),
"Connection: close",
);
$ch = curl_init(); 
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
// set url 
curl_setopt($ch, CURLOPT_URL, $url); 
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
//return the transfer as a string 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_POSTFIELDS, array("xml"=>$xml));
// Check if any error occurred
if(!curl_errno($ch))
{
$info = curl_getinfo($ch);
echo "<pre>";var_dump($info);
echo 'error:' . curl_error($ch);
//echo 'Took ' . $info['total_time'] . ' seconds to send a request to ' . $info['url'];
}                                   
$result = curl_exec($ch);
echo "<pre>";print_r($result);exit;