public function index(){
     
        $token = ‘token’;
        $timestamp = $_GET[“timestamp”];
        $nonce     = $_GET[“nonce”];
        $signature = $_GET[“signature”];
        $echostr   = $_GET[“echostr”];

        $tmpArr = array($token, $timestamp, $nonce);

sort($tmpArr);
        $tmpStr = implode( $tmpArr );
        $tmpStr = sha1( $tmpStr );

        if( $tmpStr == $signature ){
            echo $echostr;
        }else{
            echo false;
        }  
    }