So I have decided to take a project I have been working on, and project management system, and convert it from a standard multi-paged application to a single-page application. In the process I have looked at a number of javascript MV*ish frameworks (ember, knockout, backbone, etc...) and have decided to go with backbone.js as it seems the most flexible solution and that I already use underscore.js for both its utilities and template system.
The one biggest concern I have with doing this is the potential code duplication I am going to have for model and business/domain logic in both my PHP models and in my backbone models.
This is just a technical cost I have pay when going with an architecture like this or are there some things I can do to lessen this concern?