Dolby Headphone is it's own technology that will take in either DD or PLII. PLII isn't built into DH, just as DD isn't...
I used to use Pro Logic II on my old Pioneer surround sound system. Worked like a charm and gave a convincing surround sound cues to my speakers.
If you happen to have a Nintendo Wii and a surround sound, you'll see just how well Pro Logic II works.
Edited by Mad Lust Envy - 7/1/12 at 10:52pm