Q:

Creating a dynamic one page web application

I would like to make a web application (PHP) that will have overlay container that contain dynamic fields/forms.   
I would like the user to complete the form but not be taken away from the main part of the page.   
Imagine, browsing a website and reporting a page error into an overlay but not being taken away from the page you were reading.   
Also, is it possible to make the form multiple parts/pages, such as user clicks next button and the next part of the form is presented?  

A:

What you are looking for is called ajax. 
Using jQuery you could easily create the kind of form you want where the whole page is not reloaded upon submission. 
Going into more details, check out jQuery UI.  There a set of usually very simple to implement power tools to help create a dynamic webpage. 
So jQuery UI stuff for layout (look at tabs) and ajax through jQuery for your communication with the server (PHP). 

A:

Nice example of this type of web app here, with some useful tips:

The Future of Web Apps - Single Page Applications

