The Manchester City midfielder spent the season at Portman Road, though couldn't prevent Ipswich from avoiding relegation back to the Championship.
However, Phillips was able to show some of the best football he has over the past two years and made his appreciation for McKenna clear in a social media post on Monday.
He said: “A frustrating end to a tough season. I just wanted to say thank you Ipswich Town.Thank you to the fans for making me and my family feel so loved after a difficult two years.
“Thank you to the staff and players, an unbelievable group that I loved being around every day.
“And a special thanks to the manager, a great manager but also a great person, who’s helped me on and off the pitch in so many ways. He made me believe in myself again.
“I have no doubt Ipswich will be back where they belong very soon and I wish everyone at the club all the best.”