Doctrine is an object relational mapper (ORM) for PHP 5.2.3+ that sits on top of a powerful database abstraction layer (DBAL). One of its key features is the option to write database queries in a proprietary object oriented SQL dialect called Doctrine Query Language (DQL), inspired by Hibernates HQL. This provides developers with a powerful alternative to SQL that maintains flexibility without requiring unnecessary code duplication.

• Relation types exemplified in Doctrine YAML Files
• List of symfony CLI commands