Ferguson saw his rock-bottom team boost their npower Championship survival prospects by ending local rivals Leicester's winning spree with two spectacular late goals.
Ferguson said: "We were the better team from the off and scored a couple of outstanding goals to get the win. I can certainly go home and enjoy the rest of my birthday. It is also the first time we have come from behind to win a game all season and it was about time we produced a fightback like that."
Posh looked like being the latest additions to the Foxes recent list of scalps when Ben Marshall swept the visitors ahead seven minutes into the second period. But 21-year-old Manchester United loanee Davide Petrucci sparked a terrific turnaround when he struck his first Posh goal with a 25-yard half-volley with 16 minutes still on the clock.
And the comeback was completed with two minutes to go when Grant McCann classily fired past Kasper Schmeichel from the edge of the box following some stunning approach play involving Lee Tomlin and George Boyd.
Peterborough clawed themselves to within four points of safety, while they also boast a game in hand on their fellow relegation scrappers. And Ferguson added: "We've always had the belief in the dressing room that we can stay up and hopefully a victory like this will give that belief to the fans."
Leicester could have killed Posh off after hitting the front. Only a fine block from Mark Little denied Marshall a second before Jamie Vardy, in for the injured Chris Wood, was denied by a Bobby Olejnik wonder save.
And it was that failure to finish the job which frustrated Foxes chief Nigel Pearson as his team's automatic promotion dreams received a blow.
Pearson admitted: "There's no doubt it goes down as a missed opportunity. When you get in front in a game like this, you have to close it out and we failed. We certainly created enough good chances to do that but I felt we didn't work hard enough to keep a clean sheet at the other end.
"That is not something you will hear me say about my players too often but I felt Peterborough had more drive than us, especially after they had got themselves level. You have to give them some credit for the way they finished the match."