Doctrine Database Abstraction Layer, abstraction layer and access library for relational databases. A thin layer on top of PDO with a lot of additional, horizontal functionality. It is a powerful PHP database abstraction layer with many features for database schema introspection, schema management and PDO abstraction.

PHPPDO is a database abstraction layer over the current PHP database functions, the project is designed to offer a migration path for new applications to the PDO classes presented in PHP 5.1.

The JASPA DOM API is a full abstraction layer for cross-browser scripting. It is written in a strongly-typed language modelled on AS3, and the JASPA compiler converts it into regular JavaScript.