i'd have to argue that the creature who swallowed the PC blocks line of effect between the PC and the cleric.
swallow whole can really bite.
Channeling energy causes a burst that affects all creatures of one type (either undead or living) in a 30-foot radius centered on the cleric
A burst spell affects whatever it catches in its area, including creatures that you can't see. It can't affect creatures with total cover from its point of origin (in other words, its effects don't extend around corners).
I realize that Channel Energy isn't a spell, but I believe that it (as a magical effect) still uses the Area of Effect rules of magic, so no.
yeah, that's what i based my opinion on. since the swallowed PC entirely inside the monster, the monster is providing the PC total cover from all angles. since burst area of effects do not affect creatures with total cover, the swallowed PC would not gain benefit of channel energy.
at the same token, the swallowed PC would also not be subject to certain hostile spells like fireball or prismatic spray.
swallow whole can really bite.
I see what you did there.