"Just taking the opportunities that were presented," said Harris, who added seven rebounds and seven assists. "We had a good pop to our offence and I was able to get in-the-flow plays."
Embiid has been diagnosed with a strained left shoulder and will be evaluated again in the week.
"It's a painfully obvious bind," coach Brett Brown said. "We're missing two All-Stars. You yank that from the team and it's painful."
The Sixers swept the four-game season series from the Knicks.
Julius Randle paced the Knicks with 30 points and 10 rebounds. Maurice Harkless scored 17 points, RJ Barrett added 15 and Elfrid Payton had 18 points and 12 assists for New York, who have lost six in a row.
Josh Richardson appeared to make a three-pointer at the end of the third quarter, but the officials ruled he didn't get the shot off before the buzzer so the score remained 87-79.
Horford hit a pair of threes early in the fourth for a 100-85 Sixers advantage with 8:34 to go.
The Knicks battled back to within 107-102 with just over two minutes left after Randle hit a free throw. Harris answered with a key three-pointer, and the lead moved back to eight.
The Lakers won their seventh straight game despite giving LeBron James the night off against the worst team in the NBA.
Rookie Eric Paschall had 23 points for Golden State, who lost Draymond Green to a two-technical-foul ejection in the second quarter.
Warriors were also without Andrew Wiggins, who has a back problem.
The loss was Golden State's eighth straight overall and eighth in a row at home.
Also, Domantas Sabonis overcame early foul trouble to collect 20 points and 11 rebounds as the Indiana Pacers registered a 106-100 victory over the Portland Trail Blazers in Indianapolis.