PHP/MySQL ReFetch Data In Grid

I have a grid populated via PHP/MySQL displayed in document all working fine.

Also I have a button that when pressed will build new SQL paramaters based on certain input fields.

How do I refresh the already displayed grid data with the new SQL row set ?

You should not re-use the old grid if you want to display a different set of data. Just build a new one and put it into the same place. If you really want to reuse the old grid object there is a clear() method which returns it into initial state. After that you need to configure it the same way as the new one.