Petrucci has started both of Posh's npower Championship fixtures since joining the club on an initial month-long deal on January 9.
The 21-year-old midfielder told the club's official website: "I am very happy. I only signed for a month in the first place because it was my first loan spell.
"I didn't know what to expect. However, since the first few days I realised that I wanted to stay for longer and I am very pleased to be here until the end of the season."
Posh have also signed Tottenham youngster Alex Pritchard on loan until the end of the season.
Pritchard, 20, a reported target for Liverpool recently, has impressed for Spurs' youth and reserve sides but has yet to make a first-team appearance for the Barclays Premier League club.
Posh chairman Darragh MacAnthony said via Twitter: "Delighted to announce loan signing of Alex Pritchard from Spurs who has joined until end of season. He is a fantastic young talent.
"Myself & Gaffer watched this young lad destroy our reserve team couple weeks ago scoring 4 goals from playing left wing / right wing / attacking midfield."
- Sports & Recreation