Phil is an insane, homicidal killer and possible Satanist, who doesn't have too lovely relations with his own family, up to the point he wants to kill them all. Despite this, he tries to act innocent towards others, such as when he "picked up Steve" for hitchhiking. Even though Steve just wanted to go "across the street" which shouldn't have even taken a minute, he got stuck with Phil for at least 6 days.
In My Way or the Highway, he picks up Steve Williams in his car due to the highway running through Brickleberry Park, stopping off for a brief moment to kill his parents, and emerges soaked in blood, causing Steve to feel unnerved. During the trip, Phil uses his sister's decapitated head as a puppet which he calls a "sibling rivalry". Steve later invites him to his house where they play Uno, but not before wrecking crews arrive to get rid of the highway and unintentionally knock down the house.
It is likely he has been sent to Hazelhurst Mental Hospital.