获取一个文档 - findOne()

只搜索具有特定 ID 的一个用户的示例，你应该：

$options = ['limit' => 1];
$filter = ['_id' => new \MongoDB\BSON\ObjectID('578ff7c3648c940e008b457a')];
$query = new \MongoDB\Driver\Query($filter, $options);

$cursor = $manager->executeQuery('database_name.collection_name', $query);
$cursorArray = $cursor->toArray();
if(isset($cursorArray[0])) {
    var_dump($cursorArray[0]);
}