  In this paper it is proved that the key to understanding the ghost imaging
mystery are the crossing symmetric photon reactions in the nonlinear media.
Hence, the laws of the plane quantum mirror (QM) and that of spherical quantum
mirror, observed in the ghost imaging experiments, are obtained as natural
consequences of the energy-momentum conservation laws. So, it is shown that the
ghost imaging laws depend only on the energy-momentum conservation and not on
the photons entanglement. The extension of these results to the ghost imaging
with other kind of light is discussed. Some fundamental experiments for a
decisive tests of the [SPDC-DFG]-quantum mirror are suggested.
