Phillipe de Chagny is the brother of Raoul de Chagny. Ever since his mother and father died, he has sort of taken the young Raoul under his wing. It is he who takes Raoul to the opera for the first time.
He owns the entire DeChagny estate, being the oldest of four children - himself, two sisters, and the youngest, Raoul. He is "on terms" with La Sorelli, a performer in the opera house. He is firmly opposed to the union of his brother and Christine Daaé, and tries to stop them. As a result, he ends up on the underground lake that is Erik's domain. Erik claims that he fell out of the boat and drowned. But the Ghost has a habit of dragging intruders to the bottom of the lake. So make of it what you will. Whatever the truth, his body was found on the shores of the underground lake, on the Rue Scribe side, the morning after the disappearance of Christine.