The 33-year-old says he feels a strong bond with Stoke for offering him the chance of Premier League football when he was unwanted to requirements at Villa Park.
He said: "Their faith then was very important. It was a crossroads for me and Stoke gave me a great chance to play first-team football.
"When you are given a chance like that, you have to pay something back. I would like to think I have been doing that and hopefully that can continue.
"I am very happy here and very pleased to have got this sorted."