From the Synaxarion:
Sainted Photios, Patriarch of Constantinople, lived during the IX Century, and came from a family of zealous Christians. His father had died a martyr's death in defense of holy icons. Saint Photios received an excellent education and, having family relations with the imperial house, he occupied the position of first state secretary in the Senate. His contemporaries said of him: "He so distinguished himself with knowledge in almost all the secular sciences, that it rightfully might be possible to take into account the glory of his age and compare it with the ancients". The young successor to the throne, Michael, and the future Enlightener of the Slavs, the Equal-to the-Apostles Cyril, were taught the sciences by him. Deep Christian piety protected Saint Photios from being seduced with the charms of court life -- with all his soul he yearned towards monasticism.
In 857 the co-ruler with emperor Michael, Bardas, expelled Patriarch Ignatios from the Constantinople cathedral-see. The bishops, knowing the piety and extensive knowledge of Photios, informed the emperor about him as a man worthy to occupy the arch-pastoral throne. Saint Photios with humility accepted the proposal. Over the course of 6 days he was led through the hierarchical positions, and on the day of the Nativity of Christ he was ordained bishop with elevation to the patriarchal throne. Soon however there began discord within the Church, stirred up by the expulsion of Patriarch Ignatios from the cathedra. In the year 861 there was convened a Council for ending of the unrest, and at which was affirmed the deposition of Ignatios and the affirming of Photios as patriarch. Pope Nicholas I, the envoys of whom were present at this Council, hoped by affirming Photios as patriarch therein to subordinate him to his power, but not having received what he expected, he betrayed Photios with an anathema at a Roman Council. From that moment there began for Saint Photios, and lasting to the very end of his life, his opposition to the papal bullying and enroachment upon the Orthodox Church of the East. In 864 the Bulgarian land voluntarily converted to Christianity. The Bulgarian prince Boris was baptised as they proposed, by Patriarch Photios himself, after which Saint Photios dispatched an archbishop and priests for the Baptism of the Bulgarian people, and in the year 865 -- Saints Cyril and Methodios were dispatched for the preaching of Christ in the Slavonic language. But the partisans of the pope incited the distrust of the Bulgarians towards the preachers of the Eastern Church. The calamitous situation in Bulgaria because of an invasion by the Germans forced them to seek help in the West, and the Bulgarian prince turned to the pope with a request to send his bishops. Having arrived in Bulgaria, the papal legates began actively to affirm there Latin teachings and usages in place of the Orthodox. Saint Photios, being a firm defender of truth and denouncer of untruth, informed the Eastern Church by means of a circular letter about the deeds of the pope, indicating that the falling away of the Roman Church from its ancient Orthodoxy was not only in rituals, but also in confession of faith. A Council was convened, censuring the arrogance of the West.
In 867 Basil the Macedonian seized the imperial throne, having murdered the emperor Michael. Saint Photios denounced the murderer and did not permit him to partake of the Holy Mysteries of Christ. For this he was removed from the patriarchal throne and locked up in a monastery under guard. In his place was again put Patriarch Ignatios. A Council was convened for an investigation into the conduct of Saint Photios: this Council was made with the participation of papal legates, who demanded of the Council the signing of a document about the unconditional subordination of all the Church to the judgment of the pope. The Eastern bishops, not in agreement with this, entered into an argument with the legates. Summoned to the Council, Saint Photios answered all the accusations of the legates with silence, and only to the question of the judges as to whether he wished to repent, did he reply: "Wherefore do ye consider yourselves judges?" The opponents of Photios after long disputes gained the victory, and their judgment being baseless, they pronounced an anathema upon Patriarch Photios and the bishops defending him. The saint was sent to prison for 7 years, and by his own testimony, "he thanked the Lord, for patiently enduring His judges...".
During this period of time the Latin clergy were expelled from Bulgaria because of the arrogance of the pope, and Patriarch Ignatios sent there his bishops. In 679, after the death of Patriarch Ignatios, there was convened a Council (many fathers of the Church call it the Eighth Ecumenical), and again Saint Photios was acknowledged as the lawful pastor of the Church. Pope John, knowing Photios personally, through his envoys declared at the Council the annulling of all the former papal decisions about Photios. The Council acknowledged the inalterable invariability of the Nicean-Constantinople Creed, rejecting the Latin distortion ("filioque"), and it acknowledged the independence and equality of both thrones and both Churches (Western and Eastern). The Council decided to abolish in Bulgaria church usages and rituals introduced by the Latins, which ended their governance there.
Under emperor Basil's successor, Leo, Saint Photios again suffered through false denunciations, being accused of speaking against the emperor. Again deposed from his cathedral-see in the year 886, the saint finished his days at the Armoneia monastery in 891.
The Orthodox Church venerates Saint Photios as a zealous defender of the Orthodox East from domination by the pope, and as a theologian, leaving behind him various works, exposing the errors of the Latins, refuting various heresies, explicating Holy Scripture, and exploring various topics of the faith.
Troparion of St Photios the Great (Tone 5):
As a radiant beacon of wisdom hidden in God,
and a defender of Orthodoxy revealed from on high,
O great Photios, adornment of Patriarchs,
thou dost refute the innovations of boastful heresy,
O light of the holy Church,
preserve her from all error,
O luminary of the East.
Kontakion of St Photios the Great (Tone 8):
With garlands of chant let us crown the Church's far-shining star,
the God-inspired guide of the Orthodox,
the divinely sounded harp of the Spirit and steadfast adversary of heresy
and let us cry to him: Rejoice, O most venerable Photios.