The son of Simon Yorke (1696—1767) and Dorothy (1717-1787), he was born at Erddig, not far from Wrexham (Denbighshire, Wales). He was related to Philip Yorke, first earl of Hardwicke, who was uncle to Simon's father Simon Yorke. His mother Dorothy was a daughter of Matthew Hutton of Newnham, Hertfordshire.After receiving his basic education in Wanstead and Hackney, he went to Eton College and subsequently to Benet College, Cambridge, where he was awarded an MA degree (1762-1765). He proceeded to Lincoln’s Inn in 1762 and was ‘called to the bar’ in 1767. He took great delight in classical literature and became a fellow of the Society of Antiquaries in 1768.

In 1770, Philip maried his first wife Elizabeth, daughter of Sir John Cust, and he had 2 daughters and 5 sons with her. Through his wife's aid he became a member of parliament and served in this capacity for the borough of Helston, Cornwall, until 1781. Elizabeth died two years previously (1779).

In 1782, Philip married his second wife, the Welsh widow Diana (d. 1805), who was a daughter of Piers Wynne of Dyffryn Aled. They had 2 daughters and 4 sons. Yorke later obtained a seat in parliament for Grantham but after a year relinquished it to his eldest son Simon (1792-3).

The marriage sparked in him a growing interest for Welsh history and genealogy, a subject for which he formerly cared very little. He began to take a keen interest in the ancestors of his wife, a descendant of Marchudd ap Cynan, lord of Uwch Dulas and said that he had come to "think the race of Cadwallon more glorious than the breed of Gimcrack", as he wrote in his Tracts of Powys. This was his first book on Welsh history and genealogy, which was published in 1795. He is known above all for writing a considerably longer work, The Royal Tribes of Wales, published in 1799 (see below).

Yorke died in 1804, followed by his wife Diana in 1805. His public performances in high-level politics are said to have been rather restrained and according to C. J. Apperley, he was "one of the worst-dressed men in the country" as well as an incompetent horseman. He was nevertheless a noted conversationalist and storyteller and achieved a measure of fame for his performances as an amateur actor at the Wynnstay Theatre.

His first genealogical book, the Tracts of Powys, was published in 1795, with 70 copies in print. Dedicated to Thomas Pennant of Downing, it was based on a limited range of printed sources as well as on correspondences with scholars such as Walter Davies. The work details the history of the descendants of Bleddyn ap Cynfyn, offers a stern critique against Polydore Virgil’s negative appraisal of the early Britons and devotes some space to the crown lordships of Powys. The appendix includes letters by Goronwy Owen and Lewis Morris.

The Tracts of Powys formed the basis for a considerably larger and much better known work, his The Royal Tribes of Wales, which was published in 1799. It was written with some help from Walter Davies and set out to give an account of the so-called 'Five Royal Tribes of Wales' and the noble pedigrees which sprang from them. Yorke was initially sympathetic to the origin myth of the Welsh people, including the traditions which traced its descent from Trojan forebears, but later rejected such theories.

Yorke also worked on a history of 'the Fifteen Common Tribes of Wales', but never lived to complete it.