PEAR MDB2 is a merge of the PEAR DB and Metabase php database abstraction layers.

3.1.1 2017-12-05 18:20 UTC

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Last update: 2020-06-26 19:59:52 UTC


PEAR MDB2 is a project to merge PEAR DB and Metabase into one DB abstraction layer.

For mor information about these projects, see:

At these URLs you will also find the licensing information on these two projects along with the credits.

Actually MDB2 is the second major version of MDB. The main differences between the new MDB2 and the old MDB version is that the API has been drastically refactored to clean up the API and improve performance.

If you have any questions or suggestions you can contact Lukas Smith. The project's co-author is Christopher Linn.

Or even better post a message to the mailinglist for development related questions of the MDB2 package itself. For questions using MDB2 pelase direct your questions to


MDB2 provides a common API for all support RDBMS. The main difference to most other DB abstraction packages is that MDB2 goes much further to ensure portability. Among other things MDB2 features:

  • An OO-style query API
  • A DSN (data source name) or array format for specifying database servers
  • Datatype abstraction and on demand datatype conversion
  • Portable error codes
  • Sequential and non sequential row fetching as well as bulk fetching
  • Ordered array and associative array for the fetched rows
  • Buffered and Unbuffered fetching
  • Prepare/execute (bind) emulation
  • Sequence emulation
  • Replace emulation
  • Limited Subselect emulation
  • Row limit support
  • Transactions support
  • Large Object support
  • Index/Unique support
  • Extension Framework to load advanced functionality on demand
  • Table information interface
  • RDBMS management methods (creating, dropping, altering)
  • RDBMS independent xml based schema definition management
  • Altering of a DB from a changed xml schema
  • Reverse engineering of xml schemas from an existing DB (currently MySQL and PgSQl)
  • Full integration into the PEAR Framework
  • PHPDoc API documentation

Getting Started

I would first recommend taking a look at docs/example.php. This should give you a general feel of how to interact with MDB2.

After that you may want to take a look at the API. There you will also find a document describing the XML schema format and a little tutorial (it was just recently ported from Metabase, so it may contain errors).

Package Content

As a user the only PHP script you will need to include is MDB2.php which will install to your PEAR root directory. All other files and their containing classes will be included via MDB2::factory(), MDB2::connect(), and MDB2::singleton().

These will load additional classes. Most classes are loaded on demand.

Furthermore MDB2 provides an extensive testing framework that works through a browser and command line interface. There are several other test that test the two wrappers. These files will install into your test dir found in the PEAR root dir.


The entire public API and most of the private methods (except for some of the large object classes) have been documented with PHPDoc comments. Most of the API is borrowed from ext-pdo, so you can look there for detailed documentation.


For most of the tests you can set the username/password/hostname in the relevant config file. The user will need to have the right to create new databases.

test.php/clitest.php/testchoose.php is the native testing suite provided by MDB2. Please see the README in the tests directory for details.

example.php contains several test calls to MDB2's native API. It requires the PEAR::VAR_Dump package and is configured to use the following settings:

username = metapear
password = funky
hostname = localhost

How to Write New Drivers

Skeleton drivers are provided in the docs directory of the MDB2 package.

The best course of action would be to take a MDB2 driver and hack it to fit the new RDBMS. This will surely be faster and it will ensure that the new driver takes full advantage of the MDB2 framework. I would however recommend working with the existing Metabase driver for inspiration that RDBMS when doing those changes.

In order to check compliance of the driver with MDB2 you can use the testing suite (see the testing section above)


MDB was started after Manuel broad be into the discussion about getting the features of Metabase into PEAR that was going on (again) in December 2001. He suggested that I could take on this project. After alot of discussion about how when and if etc I started development in February 2002.

MDB2 is based on Metabase but has been reworked severely to better match the PEAR DB API and PEAR CS. The approach I have taken so far is to take DB.php from PEAR DB and make it create a Metabase object. I have changed the Metabase structure slightly. The formatting has been reworked considerably to better fit the final structure (MDB standalone with a BC-wrapper for Metabase and PEAR DB), to fit the PEAR CS and to make it easier for other people to contribute.

The metabase_interface.php was been renamed to metabase_wrapper.php and now only serves as a wrapper to keep BC with Metabase. A wrapper will have to be created for PEAR DB as well.

Basically the result is a Metabase that is really close to the PEAR DB structure. I have also added any missing methods from PEAR DB. Work on moving the error handling to PEAR error handling is under way but still needs some work.

In MDB2 the API was heavily refactored to be even more streamlined. Redundant features have been removed. Some features where moved out of the core into separate loadable modules. Instead of resources resultsets are now wrapped into objects similar to PEAR DB.


I would especially like to thank Manuel Lemos (Author of Metabase) for getting me involved in this and generally being around to ask questions. I would also like to thank Tomas Cox and Stig S. Bakken from the PEAR projects for help in undertstanding PEAR, solving problems and trusting me enough. Paul Cooper for the work on the pgsql driver. Furthermore I would like to thank Alex Black for being so enthusiastic about this project and offering binarycloud as a test bed for this project. Christian Dickmann for being the first to put MDB to some real use, making MDB use PEAR Error and working on the XML schema manager.

Finally Peter Bowyer for starting the discussion that made people pick up this project again after the first versions of what was then called "metapear" have been ideling without much feedback. I guess I should also thank BackendMedia (my company :-) ) for providing the necessary means to develop this on company time (actually for the most part my entire life is company time ... so it goes)