A reflecting cell allowing the dynamic and independent control of the reflection phase of two perpendicular linearly-polarized waves is presented. This capability is useful for the implementation of dual-polarized beam-reconfigurable reflectarrays, as well as for new reflector functionalities such as linear/circular polarization-flexibility and polarization-twisting with simultaneous phase control. The concept is demonstrated on a unit cell operating at 8 GHz, using surface-mounted diodes. In addition to its polarization capability, the cell implements a new concept to overcome the usual tradeoff between phase range and loss in monolayer reflective cells, using a combination of PIN and varactor diodes. For each linearly-polarized component, a dynamic phase range over 360?? is achieved at 8 GHz under normal incidence, with 4 dB and 2 dB of maximum and average loss, respectively. The modeling of the cell in a general periodic environment, along with measurements in a waveguide simulator, show that similar performance is preserved within a 5% bandwidth and under TE and TM oblique incidences up to 45??. The cell size is only 0.42?? at 8 GHz.