Just some MongoDB PHP API Weirdness I guess?

mongo.php

<?php
$mongo = new \MongoClient();
$col = $mongo->testDb->testCollection;
$col->drop();
$col->insert(['test' => 'one']);

// works perfectly
var_dump(iterator_to_array($col->find([
    'test' => 'one',
], ['test'])));

// requires fields to be `fieldName => true/false`
var_dump($col->findAndModify([
    'test' => 'one',
], [
    '$set' => ['test' => 'two'],
], ['test' => true], [
    'upsert'    => true,
    'new'       => true,
]));