The Doctrine database abstraction & access layer (DBAL) offers a lightweight and thin runtime layer around a PDO-like API and a lot of additional, horizontal features like database schema introspection and manipulation through an OO API.
The fact that the Doctrine DBAL abstracts the concrete PDO API away through the use of interfaces that closely resemble the existing PDO API makes it possible to implement custom drivers that may use existing native or self-made APIs. For example, the DBAL ships with a driver for Oracle databases that uses the oci8 extension under the hood.
The Doctrine 2 database layer can be used independently of the object-relational mapper. In order to use the DBAL all you need is the Doctrine\Common and Doctrine\DBAL namespaces. Once you have the Common and DBAL namespaces you must setup a class loader to be able to autoload the classes:
<?php use Doctrine\Common\ClassLoader; require '/path/to/doctrine/lib/Doctrine/Common/ClassLoader.php'; $classLoader = new ClassLoader('Doctrine', '/path/to/doctrine'); $classLoader->register();
Now you are able to load classes that are in the /path/to/doctrine directory like /path/to/doctrine/Doctrine/DBAL/DriverManager.php which we will use later in this documentation to configure our first Doctrine DBAL connection.