PDO is a common interface to different databases that must be used with database-specific PDO driver to access a specific database server: PDO extension does not provide a database abstraction by itself, does not rewrite SQL, database emulate missing features, or perform functions using its own database. He did the same role as other classic database abstraction layer such as ODBC and JDBC: the query abstraction layer that abstracts the mechanism for accessing databases and manipulating returned records; any database driver that implements the PDO interface can expose database-specific features as regular extension functions.