Philip Stein attended the Normal College School in Cape Town and passed the matriculation examination of the University of the Cape of Good Hope in 1906. Continuing his studies at the South African College, Cape Town, he was awarded the BA degree with honours in applied mathematics by the university of the Cape of Good Hope in 1909. By 1915 he was working in the Audit Department of the South African Railway Offices in Johannesburg, but in about 1917 joined the staff of the South African School of Mines and Technology, Johannesburg (from 1923 the University of the Witwatersrand). By this time he was a member of the South African Geographical Society and was scheduled to address its members in 1918 on 'Cosmic theories'. He also became a member of the South African Association for the Advancement of Science in 1917. In about 1918 he moved to the Natal University College in Pietermaritzburg (from 1950 the University of Natal). At some time before 1932 he obtained a PhD degree.
Stein was appointed professor of mathematics and applied mathematics at the college's newly established Durban campus in 1931, a position he held until 1955. During these years he produced several papers: 'Note on a new type of continuously variable inductance of fixed resistance' (as co-author of H. Clark*; South African Journal of Science, 1932); 'On a theorem of M. Riesz' (1933) and 'On the solution of linear simultaneous equations by iteration' (with R.L. Rosenberg, 1948) in the Journal of the London Mathematical Society; 'The convergence of Seidel iterants of nearly symmetric matrices' (MTAC, 1951); and 'Some general theorems on iterants' (Journal of Research of the National Bureau of Standards, 1952). The latter paper was a report on a study of the properties of square matrices, performed under a contract between the American National Bureau of Standards and the University of California. While still at the Durban Campus of the University of Natal at this time, Stein was affiliated also with the University of California at Los Angeles.