Senior developers are not a guarantuee that the code will be good. it is likely, whenever new "senior" developers will start, they want to dump all code and write it new - this is always the same story. Instead of relying on 2 senior , developers, rely on the most popular framework for writing apps, such as YiiFramework (recommended), CakePHP, Symfony or whatever. Starting an app like this without any framework as a basis is economical suicide nowadays...