Catalysis of the reaction: 2,6-dioxo-6-phenylhexanoate + NADP+ = 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate + H+ + NADPH.
2-hydroxy-6-oxo-phenylhexa-2,4-dienoate (reduced nicotinamide adenine dinucleotide phosphate) reductase activity