PHOENIX — This was the first time all pandemic season the Knicks played in front of a real, live, half-packed, hostile crowd.

They didn’t handle it well. They blew a seven-point lead late in the third quarter. Taj Gibson and Julius Randle later lost their composure. And the powerhouse Suns routed the Knicks, 128-105, before a boisterous crowd of 8,063 — the NBA season’s largest — at Talking Stick Arena on Friday night.

Despite the loss, the Knicks (37-30) are still half-game ahead of the Hawks in the battle for the No. 4 seed in the Eastern Conference.

All the frustration of the Knicks’ collapse boiled over midway through the fourth quarter when Gibson went after Chris Paul while the Suns guard was bringing the ball up-court. Gibson body-checked Paul to the floor like it was hockey, with seven minutes left.

Gibson was called for a flagrant foul, and Paul jawed with Knicks coach Tom Thibodeau over the infraction.

“It was a physical play,’’ Gibson said. “I talked to Chris. When you’ve played so many years, you know everybody on the job by first name. It was nothing personal it’s completion. It was a stupid foul on my end. I got to be better.’’

The downtown Phoenix arena — which is allowed to admit fans at 50-percent capacity — exploded with as much noise as this NBA season has probably heard.

Tempers were still hot in the Valley of the Sun later in the fourth, when Julius Randle and Jae Crowder had words after Randle knocked Crowder down while battling for a loose ball. Randle picked up a technical foul.

Randle, who scored just eight of his 24 points in the second half, took a shot at Crowder afterward.

“He’s just a front-runner man,’’ Randle said. “He didn’t say a word in the first half when they were down, They started making it close and he wanted to say something. That’s who he is. Everyone knows.’’

Afterward, Paul said the Gibson incident is history.

“It is what is in the heat of the game,’’ Paul said. “Me and Taj talked afterward. It’s all love.’’

RJ Barrett said before the contest, “We definitely owe them,’’ referring to the Knicks’ late loss to the Suns at the Garden on April 26.

But Barrett, despite scoring 23 points, figured into the collapse with the biggest blunder of the game. He was part of the mess when the Suns closed the third quarter with nine unanswered points, including four points in the final 1.8 seconds of the quarter.

“We’re up 88-81 with minute to go in the third,’’ Thibodeau said. “We didn’t close the quarter the way we would’ve liked. One minute the game changed. You can make the case they’re as good as any team in the West. A team like that you have to play 48 minutes.’’

Off a Derrick Rose 3-pointer, the Knicks led by seven points with one minute left in the third before the collapse.

After a basket by Frank Kaminsky and a 3-pointer by Cameron Payne pulled the Suns (48-19) within two, Randle shot an airball. Phoenix’s Devin Booker raced downcourt and blew the layup, but Torrey Craig tipped it in to tie the score.

Then came the Barrett faux pas. Barrett lackadaisically looked to inbound and had the ball stolen by Payne, who laid it in to put the Suns up 90-88 after three. It sent the crowd into a frenzy.

Crowder got hot in the fourth quarter and finished with 18 points. His second trey of the quarter, with 8:20 left, gave the Suns a 104-93 lead. That made it a 23-5 run from the time the Knicks were up by seven late in the third.

“We played a poor second half,’’ Randle said. “We got away from everything we did that made us successful.’’

After two losses, the Knicks (37-30) are 2-2 on their road trip, which will end in Los Angeles with games against the Clippers and Lakers.

They won’t face nearly this many fans at Staples Center, because Los Angeles County has stricter rules than most NBA cities.

“It’s good see the fans back in the building and it appears it’s starting to pick up,’’ Thibodeau said. “And they’re a terrific team. And they had something to cheer about.’’