I am quite new to php and are about to start developing a system that will be favoured by having a module-oriented design since new isolated/independet "services" will be added to the system over time. All will be tied together in a normal web-page where one menu entry represents one service. There may be several modules that different services use but each service will definitly need at least one of its own module.
What I would like to know is what the best practice is for creating php-application to which it will be easy to add new independent modules over time?
Thanks!