PDO (PHP Data Objects / PHP Data Objects) in a nutshell; an interface that provides lightweight and consistent access to the database. As you can see from its name, it supports dozens of database drivers with “Object Oriented Programming” interface;
- FreeTDS / Microsoft SQL Server / Sybase
- Firebird/Interbase 6
- IBM DB2
- IBM Informix Dynamic Server
- MySQL 3.x/4.x/5.x
- Oracle Call Interface
- ODBC v3 (IBM DB2, unixODBC and win32 ODBC)
- SQLite 3 and SQLite 2
- Microsoft SQL Server / SQL Azure
If you want to switch to a different database driver in the future, instead of changing your system fundamentally, you can do this job with some modifications from where you left off with PDO.
Apart from these, PDO comes from 5.1, so you will need updated versions to work.