Philip Airhart was born on December 13, 1821, in Rockingham County, Virginia. He married Lucinda Evans around 1851, and they had at least six children: John, born around 1852; Sarah, born around 1854; Elizabeth, born around 1856; Melissa, born around 1859; Jefferson Davis, born around 1863; and Nannie, born around 1866. He worked as a farmer in Augusta County, Virginia. By 1860, he owned $8,790 of real estate and $5,215 of personal property, including at least one enslaved laborer.
Airhart sided with the Confederacy during the Civil War. He received a commission as a 2nd lieutenant in Company D of the 52nd Virginia Infantry. He fell ill that fall, and he was reported absent on November 11, 1861. He returned to the regiment on February 15, 1862, but he mustered out on May 1, 1862.
He returned to Augusta County after leaving the army, and he resumed his work as a farmer. By 1870, he owned $3,000 of real estate and $500 of personal property. He remained in Augusta County for the rest of his life, and he died there in September 1902.