MongoDB\Database::getTypeMap()

<?php
$database = (new MongoDB\Client)->selectDatabase('test', [
    'typeMap' => [
        'root' => 'array',
        'document' => 'array',
        'array' => 'array',
    ],
]);
var_dump($database->getTypeMap());

array(3) {
  ["root"]=>
  string(5) "array"
  ["document"]=>
  string(5) "array"
  ["array"]=>
  string(5) "array"
}