Exposing business logic through web services and web site

How are sites like Flickr, PayPal, Amazon, Digg, etc implemented? They expose their business logic through both an interactive website and a public API.

I have been writing SOAP web services using Apache Axis2/Java but am now unclear how to integrate this with a PHP web application. Do I interact with the core through the web services or can I access it directly?

I imagine being able to access it directly would by much more efficient.

Could someone explain how this sort of architecture works?

Thanks,
Scott

As far as I understand, these things are accessed through very carefully designed layers. You would be right to assume they interact through a webservice.

I work for a company that designs and implements customer service back office software and we use java's J2EE framework. So along with that we utilize a webservice layer, which then interfaces an EJB layer and Domain/DAO layer (respectively the business logic layer and database layer). This framework, along with other popular frameworks such as Ruby On Rails, Django, Struts, etc. utilize a longstanding methodology known as MVC .

I would suggest in your case to spend some time implementing the MVC methodology (IF you have the need and the time .. and of course the interest). You could look into a php based MVC framework called Zend Framework which may or may not have some web service hooks built in (I believe it does). Once you've separated your layers out (and you can quite comfortably do this without a framework at all, dont believe all the hype), then publish your web service calls as an API to your website.

Accessing your business logic layers directly may be more efficient in the short term, but as your website/application grows in complexity this may become a liability more than an asset.