What is "doctrine-2"

Doctrine 2 is an Object-Relational Mapping Framework (or ORM) for PHP (5.3.2+). While Doctrine 1.2 uses the Active Record standard Doctrine 2 uses the Data Mapper standard. The Doctrine Project is a collection of open source libraries and tools to handle database abstraction and mapping of relational objects written in PHP.

The ORM is a development technique used to reduce the impedance of object-oriented programming using relational databases. The database tables are represented through classes and the records of each table are represented as instances of the corresponding classes.