Developing "Nth-Tier" Web Applications For Unix?

Kismet asks: "I've recently been involved in a largish Web application written using Microsoft tools. It consists of a UI layer written in VBScript for Microsoft ASP, a business tier of COM objects, and a backend on SQL Server 7. How can I implement something like this with Linux? It's really easy to use server-side COM objects with ASP, but is there anything that easy for PHP or Mason or something else on Linux? PHP's database stuff is neat, but I'd like to move that out of the site script."