MDB2 is a merge of the PEAR DC and the Metabase PHP database abstraction layers. You can read more about it at http://pear.php.net/package/MDB2.
To install the package, SSH in to your server as root and run this command:
sudo pearX.Y-sp install MDB2 MDB2_Driver_mysql
You can then run the following command as root to verify the PEAR MDB2 library and its MySQL driver package are installed:
sudo pearX.Y-sp list | grep MDB2
You should see the following output:
MDB2 2.4.1 stable MDB2_Driver_mysql 1.4.1 stable