define("TOKEN", "weixin");
$wechatObj = new WXApiVerify();
/*开始验证程序*/
$wechatObj->valid();

<?php
/**
* Class WXApiVerify
*/
class WXApiVerify
{

/**
* For weixin server validation
* @param bool $return 是否返回
*/
public function valid($return=false)
{
$echoStr = isset($_GET["echostr"]) ? $_GET["echostr"]: '';
if ($return) {
if ($echoStr) {
if ($this->checkSignature())
return $echoStr;
else
return false;
} else
return $this->checkSignature();
} else {
if ($echoStr) {
if ($this->checkSignature())
die($echoStr);
else
die('no access');
} else {
if ($this->checkSignature())
return true;
else
die('no access');
}
}
return false;
}

private function checkSignature()
{
$signature = isset($_GET["signature"])?$_GET["signature"]:'';
$timestamp = isset($_GET["timestamp"])?$_GET["timestamp"]:'';
$nonce = isset($_GET["nonce"])?$_GET["nonce"]:'';
$token = TOKEN;
$tmpArr = array($token, $timestamp, $nonce);
sort($tmpArr,SORT_STRING);
$tmpStr = implode( $tmpArr );
$tmpStr = sha1( $tmpStr );
if( $tmpStr == $signature ){
return true;
}else{
return false;
}
}

}