php - 执行 Twilio 文件以在用户拨打号码时执行操作时出现解析错误

Question

我收到一个解析错误：

12100 Document parse failure
Description:vError on line 1 of document  : Premature end of file.  Please ensure that the response body is a valid XML document.

我不确定为什么会发生此错误。我的代码如下。你能告诉我这个错误的根本原因是什么。

<?php

    header("content-type: text/xml");
    require "twilio-php-latest/Services/Twilio.php";
    $server= "http://ea3473a.ngrok.com";
        /* Set our AccountSid and AuthToken */
    $AccountSid = "AC043519349d0042fc190fe61870e591cd";
    $AuthToken = "19b05608d0e1b9b7ccda615f6620f388";
    $caller=$_REQUEST['From']; 

    echo "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
    $from= "+17864310795";
    $client = new Services_Twilio($AccountSid, $AuthToken);
    try {
            $to = $caller;            
            $url = $server.'/trial.php';
            $client->account->calls->create(
            $from, 
            $to, 
            $url,
            array( 
            'Method' => "GET", 
            'FallbackMethod' => "GET", 
            'StatusCallbackMethod' => "GET", 
            'Record' => "false", 
            ));
        } catch (Exception $e) {
            // log error
        }
?>
<Response>
     <Reject reason="busy"/>
</Response>