This organization offers an open source ORM built on PHP and PDO. It distributes the software it develops under the MIT license. It has an extremely easy to use Query Builder and DBAL.
If you wish, you can just use the DBAL library. The DBAL library comes with Query Builder, Connector and DataMapper.
composer require initorm/dbal
If you need a more advanced solution, you can choose the ORM library built on DBAL.
composer require initorm/orm