我正在努力从 mongodb 迁移到新的 php 驱动程序，此时我不知道问题到底是什么，查询在旧驱动程序中运行良好，实际上我没有收到任何查询或 php 错误。print_r 返回聚合 fn 的结果如下 php version : 7.1.18, Zend Engine : v3.1.0, mongo: v3.4.15
> MongoDB\Driver\Cursor Object (
> [database] => demoDb
> [collection] =>
> [query] =>
> [command] => MongoDB\Driver\Command Object
> (
> [command] => stdClass Object
> (
> [aggregate] => app_button
> [pipeline] => Array
> (
> [0] => stdClass Object
> (
> [$match] => stdClass Object
> (
> [location] => stdClass Object
> (
> …