The deal is for $17.5 million with a maximum value of $24.5 million, a league source told ESPN NFL Insider Adam Schefter. Porter will make $1.5 million in 2010, $6 million in 2011 and $6 million in 2012.
With 92 career sacks, Porter trails only Jason Taylor (127½) among active players. Porter has 12 career interceptions, including one returned for a touchdown, 23 forced fumbles and nine fumble recoveries with two returned for TDs.
Porter will join a team with a coaching staff that includes several members of the Steelers' staff when he was with Pittsburgh. They include coach Ken Whisenhunt, who was the Steelers' offensive coordinator.
Porter had been courted recently by the Washington Redskins.
When he met with Cardinals officials at the team's headquarters on March 11, Porter said the familiarity with the coaches was a big reason he was considering Arizona. He also wanted to be relatively near his hometown of Bakersfield, Calif.
"I was looking to play for a West Coast team and I know everything Whiz is about," Porter said at the time. "He had me over there in Pittsburgh for eight years so I don't have to be blindsided by some new coaches and trying to wonder how I fit. I know exactly how I fit. I know how he would try and use me if I was here and I am just trying to be a piece to the puzzle that's already there."
Porter disputed the perception that, because of his declining stats with the Dolphins, he could no longer play at the elite level he had established in Pittsburgh.
"I've got a lot left," he said last week. "All you have to do is turn on the tape and I feel like I don't have to sell myself. What I did on the football field is going to sell that for me. With my role being reduced to the playing time I did have and missing three games, I still mustered up enough to lead the team [with nine sacks]."
Whisenhunt called the addition of Porter "exciting on many levels."
"Two areas that come to mind are his productivity on the field, getting 26.5 sacks over the last two years is pretty impressive, especially considering last year with not even playing a full season," Whisenhunt said. "Also the mentality he brings, it's something we have made great progress with as a team. Having another veteran player, who has had great success in this league, to contribute to that will only help us in an area defensively where we want to improve."
The Associated Press contributed to this story.