His father, Guillaume of Lagonesse, had accompanied Charles on his conquest of the Kingdom of Sicily, and died in 1269.
[1] While serving as seneschal of Piedmont, he was sharply defeated in autumn of 1275 and was forced to retreat into Provence, abandoning most of the province.
[2] His predecessor, Galeran of Ivry, had left the affairs of the principality in disarray, and Philip strove to pay off the troops stationed there and improve the fortresses with funds from the reorganized mint at Glarentza.
[3] After the Sicilian Vespers and the revolt of the island of Sicily, he was recalled from Achaea for the ensuing war.
[3] He was invested with Giffoni and Vairano in 1284; he was, in addition, Lord of Airola.