Application Dev -- Separating code for speed.

I have a application, almost like a web portal. I am working on developing a version for public use. And have run into some development questions. The application is split into 4 major parts. Plugins -- A class that can be used by one or more modules. Example: A PDF generator. Modules -- A Class of commands that do a specific task. Example: A Work flow controller. User Information -- An object that holds all the current user information including the user access levels. Portal Controller -- A main object that controls all plugins, modules, and user information. A complex Portal with complex modules can begin to slow things down, especially when you start to have 800 + users and thousands and thousands of lines of code loaded for each user. My question is this: Is there a way in PHP to have the "Portal Controller" run seperately with out needing to load or include the objects for every user? I was thinking of something like http://mysite/PortalController?Action=GetUserAccessRules Are there other ways to do this? Would this speed anything up or would it slow it down. Just trying to find a good way to keep code seperated and speed up access on large sites. Any input you could give me would be greatly appreciated. Thanks in advance, Jonathan Pitcher