XML解析错误：Twilio中文档元素之后的垃圾

I am running the following code, and it is showing me this error. Can someone tell me why is my xml giving a problem? When i run this in the browser I get:

XML Parsing Error: junk after document element

When I run this through Twiilio I get the following error

parserMessage    Error on line 2 of document : Content is not allowed in prolog.

<?php

    header("content-type: text/xml");
      echo "<?xml version=\"1.0\" encoding=\"UTF-8\"?>
";
    require "twilio-php-latest/Services/Twilio.php";

        /* Set our AccountSid and AuthToken */
    $AccountSid = "xxxxx";
    $AuthToken = "xxxx";

    include 'db.php';
    $caller=$_REQUEST['From'];
    /* Instantiate a new Twilio Rest Client */
    $client = new Services_Twilio($AccountSid, $AuthToken);

    $from= "+17864310795";
    $student_number=substr($caller,1);
        $db = new PDO("mysql:host=localhost;dbname=xxxx","xxxx","xxxx");
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $studentData=getSingleStudentData($db,$student_number);
    foreach($studentData as $key=>$val)
    {
        $student_id=$val['student_id'];
        $phone=$val['phone_number'];
        $status=$val['status'];
        echo $student_id;
        // find out last call successfully completed by the student
        if($status==1)
        {
            $progress = getLastActivity($db,$student_id);
X
X
X
echo "done with initialize<br/>";
            $server= "http://sample.com";


        try {
            $to = '+' . $phone;            
            echo $phone;
            $questions_id_url='questions_id_0='.$questions_id[0].'&questions_id_1='.$questions_id[1].'&questions_id_2='.$questions_id[2];
            $questions_file_url='questions_file_0='.$questions_file[0].'&questions_file_1='.$questions_file[1].'&questions_file_2='.$questions_file[2];
            $url = $server.'/startCall.php?call_id='.$call_id.'&phone='.$phone.'&'.$questions_id_url.'&'.$questions_file_url.'&student_id='.$student_id.'&story='
            .$story.'&story_id='.$story_id.'&call_number='.$call_number.'&question_number=0&count_english=0&count_hindi=0&insert_receivecall=0';
            echo "here"."-----".$url;
            $client->account->calls->create(
            "+17864310795",
            $to,
            $url,
            array(
            'Method' => "GET",
            'FallbackMethod' => "GET",
            'StatusCallbackMethod' => "GET",
            'Record' => "false",
            ));
        } catch (Exception $e) {
            // log error
        }
        }
    }
?>
<Response>
     <Reject reason="busy"/>
</Response> 

I have tried everything, and was hoping I could spot the error

Twilio developer evangelist here.

I think your problem is that you're pushing out more than just XML within that script. You start by setting the content type to XML and echoing the XML declaration, but after that you start to echo what looks like debugging commands, which aren't valid XML, so the parser throws an error.

So, to start, I would comment out or remove anything that echos non XML content from your script.

Let me know if that helps.