a page reload every action is very very very annoying.. i know this is a php board... but you might be better off with a java applet
you could use a trick with javascript... have javascript load a .php page in a hidden frame... or use javascript to load an image, which is actually a .php script that returns an image...
you can then use that info to have the page reposition dhtml-like the stuff on the board...
how much of the game stuff have you thought through already... i haven't, so the above is my un-attempted opinion...