Yes, PHLEGM is a Scrabble word!

Letter values in Scrabble US: P 3, H 4, L 1, E 1, G 2, M 3.

Is it a valid word?

PHLEGM is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

apathy demonstrated by an absence of emotional reactions
expectorated matter; saliva mixed with discharges from the respiratory passages; in ancient and medieval physiology it was believed to cause sluggishness
inactivity; showing an unusual lack of energy

Not playable in Scrabble US: UNEMOTIONALITY.