Over the last few years while working for clients building content management systems I developed a system, or framework, of PHP scripts that aid in centralizing the core of the web application into one spot. This isn't a traditional MVC framework with countless scripts and folders. It's merely a handful of php files and organizational method that allows one to get an API up and running that powers both their internal (backend) and external (frontend). Inspired from using the Flickr REST api, I developed a similar system that worked for me and more importantly worked for the website in a robust manner.

Besides using a certain structure, config file, and helper functions within your php classes, you are allowed to code the SQL and logic the way you want to code it.

Versions of this system have been used on:
comedyfetish.com
iamspecialized.com
theheadsofstate.com