Photon equations are different from the Newtonlike ones: there is no force term to accelerate a photon, etc. Its energy is calculated differently: hv. So speaking of photon mass is senseless. What we need to know is how photons are created and how they exchange the energymomentum with matter. The theory of that does not contain any mass belonging to photon. Moreover, the relativistic relationship between the photon energy and momentum is valid only for m=0.
