Harry Feucks has a new post on the SitePoint PHP Blog today that talks about the integration of PHP applications - specifically some ideas put forward by a paper on the subject by one of the Gallery2 team.

Anyway, this is basically a short "research paper" written by one of the Gallery2 development team on how to do web application integration. In case you were wondering Gallery is a (perhaps the most) popular PHP image gallery application. Gallery2 is a complete re-write and was released last autumn.

Returning to integration, this is area which has yet to be well solved IMO, either in PHP or other web platforms. The basic requirement often stems from "How do I provide my sites visitors a single signon to my forum / wiki / blog / gallery etc.?"

He mentions a few key aspects of the integration, including "Master-Slave relationship and Communication", "Session management", "URL generation", "Controlling Access", and "Namespace Collisions". For each of these, though, he allows the paper to speak for itself. He also takes a brief look at the "where" of application integration - where the large majority of the work should happen to make the union work.