  We use the variational approach to investigate periodic measures for a class
of SPDEs with regime-switching. The hybrid system is driven by degenerate
L\'{e}vy noise. We use the Lyapunov function method to study the existence of
periodic measures and show the uniqueness of periodic measures by establishing
the strong Feller property and irreducibility of the associated
time-inhomogeneous semigroup. The main results are applied to stochastic porous
media equations with regime-switching.
