I have a photocopy of the original record from the official book of the Town of West Greenwich for 1851, p. 77. They were married on 25 Nov 1849 by Caleb Green, Minister of the Gospel, and the marriage was recorded by John James, Town Clerk, about a year and a half later. The minister, Elder Caleb Green(e) (elsewhere it is spelled with a final "e"), was married to Lucetta Nichols, daughter of Susanna Whitford and Ambrose Nichols.
These are Philip's second and third marriages; I haven't yet discovered who Philip's first wife was. The third marriage entry says he was widowed, she was divorced.
In the 1880 Federal Census, Philip R. Johnson is living in Coventy, RI, with his four-year-old son, William R. Johnson.