Was he the Philip listed as a son in the will of Philopena Byerly in 1903?
Attached is the estate index summary from Allegheny County Proceedings Index Volume 16 along with the will from Book 80. Note on the index that there were subsequent court filings for her estate, namely the inventory, property sale and the administrator's final account closing out the estate.
These scans come from familysearch.org, which has digitized some of Allegheny County's probate records:
https://familysearch.org/pal:/MM9.3.1/TH-1942-28782-27930-99...In the event that a child died after the will, her will directs the administrator to give that child's share to the remaining siblings. If Philip died in the year or two after this will, I'd bet that these documents mention his death date and detail his share going to his siblings. I would guess that the remaining court records shown in that index are either still in Allegheny County's probate court or are available at the State Archives.
Hope this helps,
Scott