When the phantom is fully manifested, the spiritualist can change the form of the phantom's manifestation (either from ectoplasmic to incorporeal or vice versa) as a full-round action that provokes attacks of opportunity.
So if the spiritualist is standing back a safe distance, but the phantom is in melee, and the spiritualist takes a full-round action to change the phantom's phase, does the phantom provoke an AoO, the spiritualist only, or both?