For the past year I have been working on a series of applications all based on the Zend framework and centered on a complex business logic that all applications must have access to even if they don't use all (easier than having multiple library folders for each application as they are all linked together with a common center).

Without going into much detail about what the project is specifically about, I am looking for some input (as I am working on the project alone) on how I have "grouped" my code. I have tried to split it all up in such a way that it removes dependencies as much as possible.

I'm trying to keep it as decoupled as I logically can, so in 12 months time when my time is up anyone else coming in can have no problem extending on what I have produced.

Example structure:

applicationStorage\ (contains all applications and associated data)
applicationStorage\Applications\ (contains the applications themselves)

applicationStorage\Applications\external\ (application grouping folder) (contains all external customer access applications)
applicationStorage\Applications\external\site\ (main external customer access application)
applicationStorage\Applications\external\site\Modules\ 
applicationStorage\Applications\external\site\Config\
applicationStorage\Applications\external\site\Layouts\
applicationStorage\Applications\external\site\ZendExtended\ (contains extended Zend classes specific to this application example: ZendExtended_Controller_Action extends zend_controller_Action )
applicationStorage\Applications\external\mobile\ (mobile external customer access application different workflow limited capabilities compared to full site version)

applicationStorage\Applications\internal\ (application grouping folder) (contains all internal company applications)
applicationStorage\Applications\internal\site\ (main internal application)
applicationStorage\Applications\internal\mobile\ (mobile access has different flow and limited abilities compared to main site version)

applicationStorage\Tests\ (contains PHP unit tests)

applicationStorage\Library\
applicationStorage\Library\Service\ (contains all business logic, services and servicelocator; these are completely decoupled from Zend framework and rely on models' interfaces)
applicationStorage\Library\Zend\ (Zend framework)
applicationStorage\Library\Models\ (doesn't know services but is linked to Zend framework for DB operations; contains model interfaces and model datamappers for all business objects; examples include Iorder/IorderMapper, Iworksheet/IWorksheetMapper, Icustomer/IcustomerMapper)

(Note: the Modules, Config, Layouts and ZendExtended folders are duplicated in each application folder; but i have omitted them as they are not required for my purposes.)

For the library this contains all "universal" code. The Zend framework is at the heart of all applications, but I wanted my business logic to be Zend-framework-independent. All model and mapper interfaces have no public references to Zend_Db but actually wrap around it in private.

So my hope is that in the future I will be able to rewrite the mappers and dbtables (containing a Models_DbTable_Abstract that extends Zend_Db_Table_Abstract) in order to decouple my business logic from the Zend framework if I want to move my business logic (services) to a non-Zend framework environment (maybe some other PHP framework).

Using a serviceLocator and registering the required services within the bootstrap of each application, I can use different versions of the same service depending on the request and which application is being accessed.

Example: all external applications will have a service_auth_External implementing service_auth_Interface registered.

Same with internal aplications with Service_Auth_Internal implementing service_auth_Interface Service_Locator::getService('Auth').

I'm concerned I may be missing some possible problems with this.

One I'm half-thinking about is a config.ini file for all externals, then a separate application config.ini overriding or adding to the global external config.ini.

If anyone has any suggestions I would be greatly appreciative.

I have used contextswitching for AJAX functions within the individual applications, but there is a big chance both external and internal will get web services created for them. Again, these will be separated due to authorization and different available services.

\applicationstorage\Applications\internal\webservice 
\applicationstorage\Applications\external\webservice