php - Yar 报错 Yar_Client_Protocol_Exception

根据鸟哥博客上Yar的介绍，书写示例时，报Yar_Client_Protocol_Exception错误，Google和Baidu都没有查到解决办法，各位大侠有没有知道的呢？

yarServer.php

class API {
    public function hello ($param = '')
    {
        return $param;
    }
    protected function hello2 ()
    {
    }
}
$service = new Yar_Server(new API());
$service->handle();

yarClient.php

SetOpt(YAR_OPT_CONNECT_TIMEOUT, 1000);
//Set packager to JSON
$client->SetOpt(YAR_OPT_PACKAGER, "json");
$result = $client->hello('zhangsan');

错误详情

Warning: [Debug Yar_Client 15:48:0.982003]: 2204859703: call api 'hello' at (r)'http://yar.demo.com/yarServer.php' with '1' parameters in /home/liuruntao/YarRPC-Demo/public/yarClient.php on line 10
Warning: [Debug Yar_Client 15:48:0.982082]: 2204859703: pack request by 'JSON', result len '53', content: '{"i":2204859703,"m":"hello","p":' in /home/liuruntao/YarRPC-Demo/public/yarClient.php on line 10
Fatal error: Uncaught exception 'Yar_Client_Protocol_Exception' with message 'malformed response header '
Warning: [Debug Yar_Server 15:4'' in /home/liuruntao/YarRPC-Demo/public/yarClient.php:10
Stack trace:
#0 /home/liuruntao/YarRPC-Demo/public/yarClient.php(10): Yar_Client->__call('hello', Array)
#1 /home/liuruntao/YarRPC-Demo/public/yarClient.php(10): Yar_Client->hello('zhangsan')
#2 {main}
  thrown in /home/liuruntao/YarRPC-Demo/public/yarClient.php on line 10