Following a consultation earlier today veteran prop John went under the knife for treatment to a longstanding knee cartilage issue.
Scarlets Head of Medical Andrew Walker said: "Phil has had a longstanding on-going issue with his right knee that was more problematic after Saturday's game.
"For the health of his knee it was decided that taking the surgical route was the best option.
"We expect Phil to make a full recovery but is likely to be out for up to 8 weeks."
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland