php-selenium使用中遇到的问题

今天初次使用facebook/php-webdriver 做自动化测试
所有的安装配置完成后，
运行Facebook自带的example.php (https://github.com/facebook/p... )
直接报错，错误信息如下：
Fatal error: Uncaught exception 'FacebookWebDriverExceptionWebDriverCurlException' with message 'Curl error thrown for http POST to /session with params: {"desiredCapabilities":{"browserName":"chrome","platform":"ANY"}} Resolving timed out after 5542 milliseconds' in /Users/Yuki/Desktop/php-web/vendor/facebook/webdriver/lib/Remote/HttpCommandExecutor.php:284 Stack trace: #0 /Users/Yuki/Desktop/php-web/vendor/facebook/webdriver/lib/Remote/RemoteWebDriver.php(120): FacebookWebDriverRemoteHttpCommandExecutor->execute(Object(FacebookWebDriverRemoteWebDriverCommand)) #1 /Users/Yuki/Desktop/php-web/example.php(15): FacebookWebDriverRemoteRemoteWebDriver::create('http://localhos...', Object(FacebookWebDriverRemoteDesiredCapabilities), 5000) #2 {main} thrown in /Users/Yuki/Desktop/php-web/vendor/facebook/webdriver/lib/Remote/HttpCommandExecutor.php on line 284

报错后，验证了一下 确认curl是可以正确使用的

环境：mac+firefox+PHP 5.6.28

求有经验的人告之或帮忙分析一下，感激不尽