The scrum-half believes that continuing to play for Wales could affect his club career.
The 30-year-old told the Daily Mail: "It may well be that if I want to play on at club level, I'll have to call time on my international career in the not too distant future.
"If [Saturday's 41-16 win over Australia] is to be the last game of international rugby that I play, then what a way to bow out. Added to that, Wales fought back to win the Six Nations last season. Who knows? I'm just glad it's the end of the season now and I can enjoy it.
"It's something I'm going to think long and hard about and I've got some decisions to make in the next year. I won't be on the next Lions tour, but five caps and three wins? I'm happy with that."
Phillips, who is entering the last year of his contract with French side Bayonne, has 77 caps for Wales.