  In this paper a technique is given to recover the classical order of the
method when explicit exponential Runge-Kutta methods integrate
reaction-diffusion problems. Although methods of high stiff order for problems
with vanishing boundary conditions can be constructed, that may imply
increasing the number of stages and therefore, the computational cost seems
bigger than the technique which is suggested here, which just adds some terms
with information on the boundaries. Moreover, time-dependent boundary
conditions are directly tackled here.
