Reply content:
How big are you talking about? Some "big" website CMS condom also passed. Front end corpse, back end dick, art girl, UI shot technician, product Wang, Project dog, DBA, ops wet, married dog teacher, body test pig.
System MVC decoupling, server by function module, database split table sub-Library, static resources Cdn,cache server, file server, data interface, deployment automation. Large web site and PHP in fact, a dime relationship is not called a large web site if it is from the beginning, large-scale general is not a large, first make a framework (whatever is what, can be used as), according to the framework to achieve the function (attention to the module of code), just come up don't design too thin frame, Changes in requirements will give you 1 months to not know your previous code, modularity is ready.
If you really want to think more about, performance considerations, leaving the point of the interface is OK.