Their crucial victory was the ideal response to the manager's harsh words following their defeat at Southampton a week ago.
Irvine's verdict was: "This was a vast improvement. We talked during the week about getting back to basics. The training has been geared around that.
"We wanted to make sure we got back to doing the things you must do to compete in this division.
"A lot of harsh words were spoken last week and this was a fantastic reaction against Ipswich by the players.
"I am delighted to be back in the fourth spot. The Championship for me has been summed up today. If you have a look down the results it tells you all you need to know about the teams in this division. Everyone can beat everyone else.
"If you approach the game right and your organisation is right, you have a chance of winning. If you are just missing an edge, you will lose.
"I didn't think that we had done enough at 3-1 to win the game. But we had got ourselves a bit of breathing space.
"I thought that Kevin Lisbie was offside for one of the Ipswich goals. I felt we could easily have been given a freekick ourselves because Lisbie pushed Eddie Nolan over and then fell over him as he went down."
Ipswich boss Jim Magilton admitted it was a very disappointed dressing room after his team were forced to leave Deepdale empty handed.
He said: "A lot of our play was excellent. We just can't give away soft goals. Preston didn't have to work very hard for their goals.
"We looked like a side which was trying to get something out of the game. Our overall application and attitude was first class. We are going to have to continue that.
"Our level of intensity last week was such that we would not have scored them goals. From the first goal to the last, there were poor defensive errors. Yet in between I thought we were very good at times.
"We had one or two opportunities. I would have like to have seen a little bit more from the front two.
"I think we were a little bit hit and miss. On another day Kevin Lisbie could have had a hat-trick."
Magilton acknowledged that the foul by Alex Bruce on Stephen Elliott which set up Preston's penalty had been a "cardinal sin" by his player getting caught on the wrong side. Bruce brought down the player and Callum Davidson tucked away the sixth--minute penalty.
But the manager joked that Preston must hate Tommy Miller, a one time North End on-loan player, who has now scored around 10 times in 11 matches against Preston.
Miller raced through the defence to pull the Tractor Boys level after the half hour mark. Ironically he did not score during his seven appearances for Preston several years ago.
Jon Parkin restored Preston's lead just before the interval by heading over keeper Richard Wright who had rushed to the edge of his area.
Miller bagged his second goal after the hour mark with a free-kick that hit the top corner of the net. They should have left with a point but substitute Lisbie was denied by keeper Andy Lonergan and once struck the left post.
Magilton added: "I think we should have got something from the game. That is my gut feeling."