He dedicated himself to a life of monasticism and served as the keeper of the True Cross of the Saviour, a key Christian relic. Starting as the bishop of a beleaguered Christian community, he converted the majority of the Pagans by his example of humble, righteous and pious life, and by working multiple miracles.
Born into an illustrious family in Thessalonoka, he renounced the prospects of a comfortable secular life to become a monastic. He obeyed the words of Jesus Christ, giving away his possessions and travelling to Egypt to serve Him as a desert hermit. Five years later, he travelled to Palestine to live in a desert cave where he became severely ill. In a dream, he had a vision of the Golgotha in which the good thief descended from the cross to lead him to Christ, and entrusted to his keeping His Cross. The saint was healed completely after the vision.
Living in Jerusalem, he earned his bread as a shoemaker and gave away most of his earnings to the poor. His humility and almsgiving made him widely known across the city, and the Bishop of Jerusalem ordained him into the priesthood. As a priest, he became the guardian of the True Cross. His vision of the Golgotha thus became true. After three years, he was elected the Bishop of Gaza.
When he became bishop, Christians were a small and persecuted minority in Gaza, and with his service and righteous life, he was working hard to change this situation. One year, when the area came under the threat of famine because of a protracted drought, he gathered all the Christians in the city and told them to fast. Then he celebrated an all-night vigil and went in procession, and on the next day, it rained. Hundreds of Pagans converted after that incident. In another miracle, as Bishop Porphirius was carrying a cross, the main temple of Aphrodite collapsed. Another several hundred unbelievers found faith after that. After 2o years of his service, Gaza became a majority Christian territory.