I have been using Zend Framework quite extensively during the last few years. On a recent project, we had 8-9 separate applications integrated into the a single website. Many of these applications used a different a databases (Oracle, MySql, etc.), so we had to set up Zend Framework to be able to connect to any database at any given time.
I am working on a project using CakePHP where I initially created JSON objects to store the data. Once I began to add the JSON data to a MySQL database, I grew weary of all the input. I decided to keep one the JSON objects as is. It was data that would never change (and a lot of data). Fortunately with CakePHP you can use multiple DataSources in a project. And the DataSources don’t have to be an actual database, you can use JSON (or XML for that mater).