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As stated, the tutorial was written for 2.4.x, but the composer.json settings proffered would install 2.3.4, which has a different enough API that basic parts of the tutorial code would fail.
Doctrine 2 ORM
Master: 
2.3: 
2.2: 
2.1: 
Master: 
Doctrine 2 is an object-relational mapper (ORM) for PHP 5.3.2+ that provides transparent persistence for PHP objects. It 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.