The Zend Framework team is pleased to announce the immediate availability of the 1.9.3 release. This release is the third maintenance release in the 1.9 series. Almost 100(!) issues have been resolved for this release, covering more than 40(!) different components. You may download it from the Zend Framework site http://framework.zend.com/download/latest
With this release, Zend_Db alters the behavior for the factory() method when it comes to adapter and adapter namespace naming. Previously, it would take any any string and normalize it so that it was in strict Ucwordlower_Ucwordlower naming convention. This has proven to be an issue with many developers that wish to use the factory to create custom adapters that do not wish to follow this naming scheme (for instance, if they desire to use MixedCasing in the various component segments). Now, in 1.9.3, Zend_Db::factory() requires developer to pass through the name from the bootstrap or configuration file to the factory for instantiation; as an example, the string "PDO_MYSQL" will not work, but "Pdo_Mysql" (which corresponds to Zend_Db_Adapter_Pdo_Mysql) will). This has the added benefit of consistency in naming and transparency between the config and the actual code.
Long story short? The actual names you use for your adapter should be the same names you use in your config and bootstrap file.