更改公众号的基本配置时，将此文件在保存至url目录下，就可以填写token值了（tooken值为define（“TOKEN”，“your token name”），其中的“your token name就是需要的token值了，可自己填写”）
<?php
/**

• wechat php test
  */
  //define your token
  define("TOKEN", "weixin");
  $wechatObj = new wechatCallbackapiTest();
  $wechatObj->valid();

class wechatCallbackapiTest
{
public function valid()
{
$echoStr = $_GET["echostr"];

    //valid signature , option
    if($this->checkSignature()){
        header('content-type:text');
        echo $echoStr;
        exit;
    }
}

public function responseMsg()
{
    //get post data, May be due to the different environments
    $postStr = $GLOBALS["HTTP_RAW_POST_DATA"];

      //extract post data
    if (!empty($postStr)){

              $postObj = simplexml_load_string($postStr, 'SimpleXMLElement', LIBXML_NOCDATA);
            $fromUsername = $postObj->FromUserName;
            $toUsername = $postObj->ToUserName;
            $keyword = trim($postObj->Content);
            $time = time();
            $textTpl = "<xml>
                        <ToUserName><![CDATA[%s]]></ToUserName>
                        <FromUserName><![CDATA[%s]]></FromUserName>
                        <CreateTime>%s</CreateTime>
                        <MsgType><![CDATA[%s]]></MsgType>
                        <Content><![CDATA[%s]]></Content>
                        <FuncFlag>0</FuncFlag>
                        </xml>";             
            if(!empty( $keyword ))
            {
                  $msgType = "text";
                $contentStr = "Welcome to wechat world!";
                $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgType, $contentStr);
                echo $resultStr;
            }else{
                echo "Input something...";
            }

    }else {
        echo "";
        exit;
    }
}

private function checkSignature()
{
    $signature = $_GET["signature"];
    $timestamp = $_GET["timestamp"];
    $nonce = $_GET["nonce"];   

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

    if( $tmpStr == $signature ){
        return true;
    }else{
        return false;
    }
}

}

?>