ADOdb is a database abstraction library for PHP. There is also a Python version; see the ADOdb for Python docs.
The PHP version currently supports an amazing number of databases, thanks to the wonderful ADOdb community: MySQL, PostgreSQL, Interbase, Firebird, Informix, Oracle, MS SQL, Foxpro, Access, ADO, Sybase, FrontBase, DB2, SAP DB, SQLite, Netezza, LDAP, and generic ODBC, ODBTP. The Sybase, Informix, FrontBase and PostgreSQL, Netezza, LDAP, ODBTP drivers are community contributions.