微信token验证代码

<?php
/**
* wechat php test
*/

//define your token
define("TOKEN", "weixin");

$signature = $_GET['signature'];
$timestamp = $_GET['timestamp'];
$nonce = $_GET['nonce'];
$echostr = $_GET['echostr'];

$token = TOKEN;
$tmpArr = array($token, $timestamp, $nonce);
sort($tmpArr, SORT_STRING);
$tmpStr = implode( $tmpArr );
$tmpStr = sha1( $tmpStr );

if( $tmpStr == $signature ){
//没加这一句一直token验证失败
header('content-type:text');
echo $echostr;
}

?>