Ajax Dropdown Menu

This is a simple project that requires AJAX, PHP, MySQL, JS and CSS. What I need is a dropdown menu, but the dropdown menu content must be getting the data from a MySQL database, and the content of the dropdown must be updated each time its dropped down. Go here for an example of what I have. [login to view URL] lets focus on the history and favorites.. I do NOT want the page to reload, thus the ajax, but each time its expanded on mouse over, the content of it needs to be updated, in case some new history or favorites has been added. somewhat like this: [login to view URL] only look like what I posted first ([login to view URL]). At any given time, new history and favorites may be added, thats why it needs to update the content (folders AND folder content) on mouse over.