设置的callback没有调用

[gaecom]

系统信息
 Hardware Overview:

      Model Name: iMac
      Model Identifier: iMac13,1
      Processor Name: Intel Core i5
      Processor Speed: 2.7 GHz
      Number of Processors: 1
      Total Number of Cores: 4
      L2 Cache (per Core): 256 KB
      L3 Cache: 6 MB
      Memory: 8 GB
      Boot ROM Version: IM131.010A.B09
      SMC Version (system): 2.9f8


PHP 7.1.1 (cli) (built: Jan 21 2017 05:37:38) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies
    with Xdebug v2.5.0, Copyright (c) 2002-2016, by Derick Rethans

yar-2.0.2$nginx -v
nginx version: openresty/1.11.2.1

yar-2.0.2$php-fpm -v
PHP 7.1.1 (fpm-fcgi) (built: Jan 21 2017 05:37:41)
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies
    with Xdebug v2.5.0, Copyright (c) 2002-2016, by Derick Rethans

\Yar_Concurrent_Client::call("http://www.f.cc/test/yar", "abc", array("parameters"), 'callback');

function callback($retval, $callinfo) {
    var_dump($retval);
}