fluxbb-database 
A lightweight wrapper around PHP::PDO, providing both SQL abstraction and an extensible query interface.
The SQL syntax abstraction we perform has 2 goals:
- Allowing portability between different DBMS.
- Allowing queries to be easily modified by hooks and/or filters before execution.
Documentation
Supported drivers / dialects
- MySQL
- SQLite 3
- PostgreSQL, from 8.4
Theoretically, it is easy (and planned for the future) to add new adapters (if supported by PDO), although some SQL abstraction might have to be rewritten.