Answer by taking a quote from the following article:

Bernard Lewis, FBA (born 31 May 1916) is a British American historian specializing in oriental studies. He is also known as a public intellectual and political commentator. Lewis is the Cleveland E. Dodge Professor Emeritus of Near Eastern Studies at Princeton University. Lewis' expertise is in the history of Islam and the interaction between Islam and the West.

In 1936, Lewis graduated from the School of Oriental Studies (now School of Oriental and African Studies, SOAS) at the University of London with a BA in history with special reference to the Near and Middle East. He earned his PhD three years later, also from SOAS, specializing in the history of Islam. Lewis also studied law, going part of the way toward becoming a solicitor, but returned to study Middle Eastern history. He undertook post-graduate studies at the University of Paris, where he studied with the orientalist Louis Massignon and earned the "Diplome des Etudes Semitiques" in 1937. He returned to SOAS in 1938 as an assistant lecturer in Islamic History.  During the Second World War, Lewis served in the British Army in the Royal Armoured Corps and as a Corporal in the Intelligence Corps in 1940-41 before being seconded to the Foreign Office. After the war, he returned to SOAS. In 1949, at the age of 33, he was appointed to the new chair in Near and Middle Eastern History.  In 1974, aged 57, Lewis accepted a joint position at Princeton University and the Institute for Advanced Study, also located in Princeton, New Jersey. The terms of his appointment were such that Lewis taught only one semester per year, and being free from administrative responsibilities, he could devote more time to research than previously. Consequently, Lewis's arrival at Princeton marked the beginning of the most prolific period in his research career during which he published numerous books and articles based on previously accumulated materials. After retiring from Princeton in 1986, Lewis served at Cornell University until 1990.  In 1966, Lewis was a founding member of the learned society, Middle East Studies Association of North America (MESA), but in 2007 he broke away and founded Association for the Study of the Middle East and Africa (ASMEA) to challenge MESA, which the New York Sun noted as "dominated by academics who have been critical of Israel and of America's role in the Middle East." The organization was formed as an academic society dedicated to promoting high standards of research and teaching in Middle Eastern and African studies and other related fields, with Lewis as Chairman of its academic council.  In 1990, the National Endowment for the Humanities selected Lewis for the Jefferson Lecture, the U.S. federal government's highest honor for achievement in the humanities. His lecture, entitled "Western Civilization: A View from the East", was revised and reprinted in The Atlantic Monthly under the title "The Roots of Muslim Rage." His 2007 Irving Kristol Lecture, given to the American Enterprise Institute, was published as Europe and Islam.

what was his job after graduating with the PHD
He undertook post-graduate studies at the University of Paris, where he studied with the orientalist Louis Massignon and earned the "Diplome des Etudes Semitiques" in 1937.