A rugged defender whose versatility served Shankly well. Ferns was born in Liverpool and grew up in Norris Green, playing for youth clubs of the Liverpool Boys' Association. He made his debut for the reserves in the 1957/58 season but wasn't able to force his way into Liverpool's first team until the 1962/63 season when he covered three times for Tommy Leishman at left-half and twice at left-back for Ronnie Moran as Liverpool returned to the top division after an eight-year absence. When the club won the League Championship for the sixth time in 1964, Ferns played in enough games, 18, to qualify for a winners' medal, filling in for Gerry Byrne, Moran and Willie Stevenson. Ferns was only selected on four more occasions the following season before being transferred to Bournemouth in August 1965. Ferns made over 100 League appearances for Bournemouth and Mansfield.

Ferns's son, also Phil, played over 200 league games for 3rd and 4th Division clubs between 1978 and 1986 before becoming a police officer. Ferns senior remained settled on the south coast and died after a short illness on 25th August 2007.