為達到程式碼不必因為DB更換而需要大幅修改，建議可以考慮使用像ADODB一類的library，聽說未來有將這種一致性存取library整合進PHP core kernel的計畫。
介紹:
PHP's database access functions are not standardised. This creates a need for a database class library to hide the differences between the different databases (encapsulate the differences) so we can easily switch databases.
We currently support MySQL, Interbase, Oracle, Microsoft SQL Server, Sybase, PostgreSQL, FrontBase, Foxpro, Access, ADO and ODBC.
PHP4 supports session variables. You can store your session information using ADODB for true portability and scalability. See adodb-session.php for more information.

Unique Features of ADODB

• Easy for Windows programmers to adapt to because many of the conventions are similar to Microsoft's ADO.
• Unlike other PHP database classes which focus only on select statements, we provide support code to handle inserts and updates which can be adapted to multiple databases quickly. Methods are provided for date handling, string concatenation and string quoting characters for differing databases.
• A metatype system is built in so that we can figure out that types such as CHAR, TEXT and STRING are equivalent in different databases.
• Easy to port because all the database dependant code are stored in stub functions. You do not need to port the core logic of the classes.
• PHP4 session support. See adodb-session.php.

Databases Supported

Name	Database	RecordCount() usable	Prerequisites	Operating Systems
access	Microsoft Access. You need to create an ODBC DSN.	N	ODBC	Windows only
ado	Generic ADO, not tuned for specific databases. Slower than ODBC, but allows DSN-less connections.	? depends on database	ADO and OLEDB provider	Windows only
ado_access	Microsoft Access using ADO. Slower than ODBC, but allows DSN-less connections.	N	ADO and OLEDB provider for Access	Windows only
vfp	Microsoft Visual FoxPro. You need to create an ODBC DSN.	N	ODBC	Windows only
ibase	Interbase 6 or earlier. Some users report you might need to use this $db->PConnect('localhost:c:\ibase\employee.gdb', "sysdba", "masterkey") to connect.	N	Interbase client	Unix and Windows
firebird	Firebird version of interbase.	N	Interbase client	Unix and Windows
borland_ibase	Borland version of Interbase 6.5 or later. Very sad that the forks differ.	N	Interbase client	Unix and Windows
informix	Informix. Still very much a beta experimental version - use at your own risk.	Y - but this is an unreliable estimate, so probably should return -1 in future versions	Informix client	Unix and Windows
mssql	Microsoft SQL Server 7. Works with Microsoft SQL Server 2000 also. Note that date formating is problematic with this driver. For example, the PHP mssql extension does not return the seconds for datetime!	Y	Mssql client	Unix and Windows. Unix install howto.
mysql	MySQL without transaction support (3.22)	Y	MySQL client	Unix and Windows
mysqlt or maxsql	MySQL with transaction support (3.23)	Y	MySQL client	Unix and Windows
oci8	Oracle 8/9. Has more functionality than oracle driver (eg. Affected_Rows). You might have to putenv('ORACLE_HOME=...') before Connect/PConnect. There are 2 ways of connecting - with server IP and service name: PConnect('serverip:1521','scott','tiger','service') or using an entry in the tnsnames.ora: PConnect('', 'scott', 'tiger', 'tnsname').	N	Oracle client	Unix and Windows
oci8po	Oracle 8/9 portable driver. This is nearly identical with the oci8 driver except (a) bind variables in Prepare() use the ? convention, instead of :bindvar, (b) field names use the more common PHP convention of lowercase names. Use this driver if porting from other databases is important. Otherwise the oci8 driver offers better performance.	N	Oracle client	Unix and Windows
odbc	Generic ODBC, not tuned for specific databases. To connect, use PConnect('DSN','user','pwd').	? depends on database	ODBC	Unix and Windows. Unix hints.
oracle	Oracle 7 or 8 support. Obsolete.	N	Oracle client	Unix and Windows
postgres	PostgreSQL which does not support LIMIT internally.	Y	PostgreSQL client	Unix and Windows.
postgres7	PostgreSQL which supports LIMIT and other version 7 functionality.	Y	PostgreSQL client	Unix and Windows.
sybase	Sybase.	Y	Sybase client	Unix and Windows. Unix hints.
db2	DB2. Warning: this is experimental. Please email me if there are problems.	Y	DB2 CLI/ODBC interface	Unix and Windows. Unix install hints.
fbsql	FrontBase. Warning: this is experimental. Please email me if there are problems.	Y	?	Unix and Windows