我正在使用QueryPath从一个网站上抓取一些数据。但是,我经常收到下面的错误消息,并且脚本终止。passed to DOMXPath::__construct() must be an instance of DOMDocument, null given, called in ....inc/QueryPath/QueryPath/CSS/DOMTraverser.php on line 417 and defined in ....inc/QueryPath
__construct() must be an instance of DOMDocument, null given, called in /var/scraper/autotrader/inc/QueryPath/QueryPath/CSS/DOMTraverser.php on line 417 and defined in /var/scraper/autotrader/inc/QueryPath