token一直验证失败，不知道为什么？
<?php
//将timestamp,nonce,token按字典序排序
$timestamp = $_GET['timestamp'];
$nonce = $_GET['nonce'];
$token = 'weixin';
$signature = $_GET['signature'];
$array = array($timestamp,$nonce,$token);
sort( $array );
//将排序后的三个参数拼接之后用shal加密
$tmpstr = implode('',$array);
$tmpstr = shal($tmpstr);
//将加密后的字符串与signature进行对比，判断该请求是否来自微信
if($tmpstr == $signature){
echo $_GET['echostr'];
exit;
}
