php中的空结果卷曲

Question

我在处理 PHP 的 cURL 时遇到问题，返回一个带有一些 URL 的空字符串 我想连接这个 api 并且我给出了空结果，任何人都可以帮助我吗？

<?php
$clTrid="TEST-23233434343";
$nictoken="6661361102210630";
$contact="Test-irnic";

$xml = '<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
<command>
<check>
<contact:info xmlns:contact="http://epp.nic.ir/ns/contact-1.0">
<contact:id>' . $contact . '</contact:id>
<contact:pw>' . $nictoken . '</contact:pw>
</contact:authInfo>
</contact:check>
</check>
<clTRID>' . $clTrid . '</clTRID>
</command>
</epp>';
$url = 'https://epp.nic.ir/submit';
$curl = curl_init($url);
curl_setopt ($curl, CURLOPT_HTTPHEADER, array("Content-Type: text/xml"));
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $xml);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($curl);
if (curl_errno($curl)) {
    $error_msg = curl_error($curl);
}
else echo " No Error ! "; 
if(curl_errno($curl)){
    throw new Exception(curl_error($curl));
}
curl_close($curl);
echo $result;
var_dump($result);
?>