MacDonald, 27, has four goals and 24 points in 63 games this season. He's played in 295 games during parts of six seasons with the Islanders, scoring 17 goals and 89 points.
"He's a good all-around defenseman," said Flyers defenseman Mark Streit, MacDonald's former teammate with the Islanders. "He plays really well defensively, blocks a lot of shots and has a really good first pass, and obviously got some offense as well. It's a really good mix and he's a great guy in the room too. He wants to win and he competes every night. As I said before he's going to make our team better."
The Islanders will receive a third-round pick in the 2014 NHL Draft and a second-round pick in 2015. Mangene, 24, has three goals and six points in 51 games this season for Adirondack of the American Hockey League.