I have application having 60+ screens in flex 3 now want to rewrite in flex 4 using states in one mxml. Is it feasible to have one large mxml??Also having remote object communication with php using zend amf.
What do you mean by one large MXML ? Do you mean that you want to have all the mxml in one class and change between views using viewstates ? If so , I would have to say that is a bad idea.
Look at breaking up your application into modules.