On DZone.com there's a new tutorial posted (by Jorge Ramon) about hooking together the models of Sencha's Touch 2 with a PHP backend to make saving data to them simpler via a proxy.

Sencha Touch models have the ability to work with a proxy. This feature allows you to save and retrieve model data from the server, memory or local storage, without depending on a Sencha Touch data store. Let's try it with a very simple scenario where the server side is a PHP page.

The article includes both the Javascript to create the models (along with its proxy and custom API methods defined) as well as the PHP that powers the backend. The PHP just reads from the "php://input" stream and echoes back out JSON, but it gives you an idea of what to expect to receive. For more information on Sencha Touch, check out their documentation.