How to make aggregation, using PHP MongoDB driver - php

Question

I use this MongoDb driver in my application. I like it, because it works well. I can run simple select and insert statements, like:
$em = new MongoDB\Driver\Manager("mongodb://localhost:27017/testdb");
$query = new Query(['name' => 'John']);
$res = $em->executeQuery('users', $query);
But the problem is, I can not find even a single example on making aggregations. PHP documentation does not say a word about this. While, MongoDb documentation seems to use another library:
$collection = (new MongoDB\Client)->test->restaurants;
$cursor = $collection->find([
'name' => new MongoDB\BSON\Regex('^' . preg_quote('(Library)')),
]);
It seems like an example from another library, because MongoDb driver does not have this MongoDB\Client class. There is such a class, but in a deprecated library. So, what is the right way to make aggregations in PHP, using modern MongoDb driver?

Answer 1

This extension provides a minimal API for core driver functionality: commands, queries, writes, connection management, and BSON serialization.
https://www.php.net/manual/en/set.mongodb.php
To execute aggregate command, use MongoDB\Driver\Command
{
aggregate: "<collection>" || 1,
pipeline: [ <stage>, <...> ],
explain: <boolean>,
allowDiskUse: <boolean>,
cursor: <document>,
maxTimeMS: <int>,
bypassDocumentValidation: <boolean>,
readConcern: <document>,
collation: <document>,
hint: <string or document>,
comment: <string>,
writeConcern: <document>
}
https://docs.mongodb.com/manual/reference/command/aggregate/#syntax