php placeholder problem?

Question

Why is the thing that comes out of my echo a %s? Instead of the string I assigned?

Complete code:
IndexAction.class.php

<?php
// 本类由系统自动生成，仅供测试用途
class IndexAction extends Action {
    public function index(){
        $this->responseMsg();
    }
    public function responseMsg(){
        $postStr="<xml>
                 <ToUserName><![CDATA[toUser]]></ToUserName>
                 <FromUserName><![CDATA[fromUser]]></FromUserName>
                 <CreateTime>1348831860</CreateTime>
                 <MsgType><![CDATA[text]]></MsgType>
                 <Content><![CDATA[tel]]></Content>
                 <MsgId>1234567890123456</MsgId>
                 </xml>";
        $postObj = simplexml_load_string($postStr);
        $fromUsername = $postObj->FromUserName;
        //echo $fromUsername;
        //echo '111';
        $toUsername = $postObj->ToUserName;
        $time = time();
        $msgType = $postObj->MsgType;
        $content = $postObj->Content;
        if($content=='tel'){
            $indexModel=new IndexModel();
            $indexModel->responseText($postObj,$content);
        }
    }
}

IndexModel.class.php

<?php
    class IndexModel extends Model{
        //回复纯文本
        public function responseText($postObj,$content) {
            $time=time();
            $fromUsername = $postObj->FromUserName;
            $toUsername = $postObj->ToUserName;
            $textTpl = "<xml>
                        <ToUserName><![CDATA[%s]]></ToUserName>
                        <FromUserName><![CDATA[%s]]></FromUserName>
                        <CreateTime>%s</CreateTime>
                        <MSsgType><![CDATA[text]]></MsgType>
                        <Content><![CDATA[%s]]></Content>
                        </xml>"; 
            echo  "textTpl is: ".$textTpl;
            $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $content); 
              //  echo $resultStr; 
        }
        
    }
?>

Answer 1

Go to browser F12 to see the redundant xml code.

Answer 2

Browsers can also parse XML, you can see it by viewing the page source code

Answer 3

You are originally the tpl of echo, there is nothing wrong with outputting %s