On his MSDN blog today Brian Swan has a new post looking at connecting PHP with the OData SDK (more on that here) to work with data over a HTTP interface/web service.
I'll start with an over simplification: OData is a protocol for creating data services that make it possible to retrieve and edit data using HTTP. More specifically, OData enables you to define a data model that lets clients address data as resources by using URIs. Data is retrieved and updated by using the HTTP actions of GET, POST, PUT, DELETE and MERGE.
He shows how to use the OData SDK for PHP to connect to a data source, build out some pre-generated classes and pull down the information from the Northwind service based on a customer ID.