<?php

require __DIR__ . '/vendor/autoload.php';

$client = new MongoDB\Client('mongodb://localhost:27070/?replicaSet=rs0');
$collection = $client->test->foo;
$collection->drop();

$it = new MongoDB\Model\CachingIterator($collection->find());

var_dump($it);
var_dump($it->count()); 

MongoDB\Driver\Exception\RuntimeException : Cannot advance a completed or failed cursor.