<?php

class Book implements MongoDB\BSON\Persistable {
    function bsonSerialize() {
        $data = get_object_vars($this);
        return $data;
    }
    function bsonUnserialize(array $data) {
        foreach ($data as $name => $value) {
            $this->{$name} = $value;
        }
    }
}

// Aux
$manager = new MongoDB\Driver\Manager('mongodb://127.0.0.1:27017');
$bulk = new MongoDB\Driver\BulkWrite;
$wc = new MongoDB\Driver\WriteConcern(MongoDB\Driver\WriteConcern::MAJORITY);
$collection = 'db.books';

// Delete previous entries
$bulk->delete([], ['limit' => 0]);
$manager->executeBulkWrite($collection, $bulk, $wc);

// Create
$book = new Book();
$book->title = 'Unnameable';
$result = $bulk->insert($book);
$result = $manager->executeBulkWrite($collection, $bulk, $wc);

// Read
$query = new MongoDB\Driver\Query(['title' => $book->title]);
$cursor = $manager->executeQuery($collection, $query);
$bookAfterInsert = $cursor->toArray();

// hack to make update work properly
// $book->__pclass = $bookAfterInsert[0]->__pclass;

// Update
$book->description = 'An interesting document';
$bulk->update(['title' => $book->title], $book);
$manager->executeBulkWrite($collection, $bulk, $wc);

// Read (again)
$query = new MongoDB\Driver\Query(['title' => $book->title]);
$cursor = $manager->executeQuery($collection, $query);
$bookAfterUpdate = $cursor->toArray();
var_dump($bookAfterUpdate[0]);

object(Book)#%d (%d) {
  ["_id"]=>
  object(MongoDB\BSON\ObjectID)#%d (%d) {
    ["oid"]=>
    string(24) "%s"
  }
  ["__pclass"]=>
  object(MongoDB\BSON\Binary)#%d (%d) {
    ["data"]=>
    string(4) "Book"
    ["type"]=>
    int(%d)
  }
  ["title"]=>
  string(10) "Unnameable"
  ["description"]=>
  string(23) "An interesting document"
}

object(stdClass)#13 (3) {
  ["_id"]=>
  object(MongoDB\BSON\ObjectID)#12 (1) {
    ["oid"]=>
    string(24) "56a05eaa5853e919c3376c31"
  }
  ["title"]=>
  string(10) "Unnameable"
  ["description"]=>
  string(23) "An interesting document"
}