This Apostle, one of the Twelve, was from Bethsaida of Galilee, and was a compatriot of Andrew and Peter. He was instructed in the teachings of the Law, and devoted himself to the study of the prophetic books. Therefore, when the Lord Jesus called him to the dignity of apostleship, he immediately sought out and found Nathanael and said to him, "We have found Him of Whom Moses in the Law and the Prophets did write, Jesus of Nazareth, the son of Joseph" (John 1.45). Having preached Jesus the God-man throughout many parts of Asia Minor, and having suffered many things for His Name's sake, he was finally crucified upside down in Hierapolis of Phrygia.
Apolytikion in the Fourth Tone
O Holy Apostle Philip, intercede with the merciful God that He grant unto our souls forgiveness of offences.
Kontakion in the Fourth Tone
Your disciple and friend, emulator of Your passion, the divinely eloquent Philip, proclaimed You to the world as God. By his entreaties, and through the Theotokos, keep Your Church from lawless enemies, O most merciful.
Source: Greek Orthodox Archdiocese of America, goarch.org/chapel/saints_view?contentid=291.