Carter Hart, who lost his seventh straight on the road, was replaced by Brian Elliott after Keller scored on the power play to make it 3-0 at 16:15.
"A couple of bad bounces, a couple of things that didn't go our way," Hart said. "It's been the story of the last couple of games on the road, we just have to overcome that first period."
Hart made nine saves, and Elliott allowed two goals on nine shots in relief.
Philadelphia (22-15-5) is 1-4-0 during a six-game road trip, allowing at least five goals in each loss.
The Coyotes went 3-1-0 during a four-game homestand after going 1-4-0 in their previous five games. They are 11-10-1 at home.
"Yeah, it's huge for us," said forward Nick Schmaltz, who had two assists. "We all talked about being better at home and we've rattled off three straight (wins), so it's good for our confidence. We want to make this place a tough place to play."
Brad Richardson scored his second goal in as many games after he had one through 35 games to start the season, making it 1-0 at 12:33 of the first. Jordan Oesterle scored 57 seconds later, his first goal in 56 games, for a 2-0 lead at 13:30.
Keller's was the fifth power-play goal allowed by the Flyers during their losing streak.
"We talk about it a lot, don't change the way you play when you're up," Coyotes forward Lawson Crouse said of their first period, which followed a three-goal third period in a 4-2 win against the Anaheim Ducks on Thursday. "Now we know when get up a couple goals, we really have to keep it going."
Crouse scored with 0.3 seconds left in the second period to make it 4-0.
Tyler Pitlick scored on the first shot against Hill to make it 4-1 at 3:00 of the third, and Keller scored his second of the game for a 5-1 lead at 4:27.
Justin Braun scored at 8:46 to cut it to 5-2. He has two goals in three games after going the first 39 games of the season without one.
Derek Stepan, who had an assist, scored shorthanded into an empty net at 17:36 for the 6-2 final.
"All four lines contributed and, again, if we play a certain (structured) style, we have a good chance to be successful," Tocchet said.