Philadelphia’s Roy Halladay delivers a pitch in the first inning to a Florida batter. Halladay pitched a perfect game Saturday in Miami.

Miami ? Stoic as always, Roy Halladay’s expression never changed.

Until the end, that is.

Until there was history — a perfect game, the marquee performance of his All-Star career.

The Philadelphia Phillies’ ace threw the 20th perfect game in major-league history, beating the Florida Marlins, 1-0, on Saturday night.

At 9:23 p.m. EDT, when he got pinch-hitter Ronny Paulino to hit a grounder to third for the 27th out, only then could Halladay bask in his moment — breaking into a big smile and wrapping his arms around catcher Carlos Ruiz before disappearing in a joyous, jumping gray-and-red mob of teammates.

“It’s never something that you think is possible,” Halladay said. “Really, once I got the two outs, I felt like I had a chance. You’re always aware of it. It’s not something that you expect.”

It was the second perfect game in the majors this month alone, unheralded Dallas Braden doing it for Oakland against Tampa Bay on May 9. It’s the first time in the modern era that there were a pair of perfectos in the same season — Colorado’s Ubaldo Jimenez threw a no-hitter, too, in April.

Halladay struck out 11, and was cheered by a crowd of 25,086 throughout much of the night. Another fan called later — Vice President Joe Biden dialed up the Phillies’ clubhouse to offer his congratulations when it was over.

“Early in my bullpen I was hitting spots more than I have been. I felt like I just carried that out there,” Halladay said.

While there were a couple of good plays behind him — shortstop Wilson Valdez went deep into the hole for a grounder, backup third baseman Juan Castro went to his knees for another, second baseman Chase Utley ranged well to his left for another fine play — Halladay didn’t need any great defensive work in this gem.

“I think everybody knows you have to have those kind of plays to do something like that,” Halladay said.

Yes, but on this night, the 33-year-old righty known as Doc was a veritable one-man show.

“You’ve got to take your hat off to Doc,” Marlins manager Fredi Gonzalez said. “That’s why he is who he is. That’s what they got him for.”

Steely-eyed, standing tall and always working swiftly, Halladay (7-3) broke into a big smile as his teammates rushed in to congratulate him.

“That’s a big emotion for him,” Phillies left-hander Jamie Moyer said, laughing in the clubhouse. “It’s fun to watch.”

The Marlins said they would give Halladay the pitching rubber as a souvenir, leading to a slightly surreal scene. The lights at Sun Life Stadium went out and fireworks began exploding two minutes after the game ended, with the field crew preparing for a postgame concert behind second base.

Working in the dark, four men went to work on the mound, digging up the slab where Halladay made history.

“Look who’s pitching,” Marlins outfielder Cody Ross said. “It’s Roy Halladay, the best pitcher in baseball. It’s not embarrassing.”

The concert lasted more than an hour.

On this night, Halladay was the lone maestro.

The former AL Cy Young winner was the centerpiece of a multiteam trade that brought him from Toronto to the two-time NL champions in the offseason, and the Phils gave him a $60 million, three-year contract extension.

He was within one out of a no-hitter on Sept. 27, 1998, in just his second major-league start, pitching for the Blue Jays against Detroit. Pinch-hitter Bobby Higginson ended that on the first pitch he saw, hitting a solo home run.

“It’s hard to explain,” Halladay said. “There’s days where things just kind of click and things happen. It’s something you obviously, you don’t ever go out and try to do. It’s a great feeling. It’s a lot better than the eight and two-thirds.”

Halladay faced three Marlins pinch-hitters in the ninth. Mike Lamb led off with a long fly ball, but Shane Victorino had plenty of time to backtrack in the super-spacious outfield at Sun Life Stadium and squeeze it for the first out.

Another pinch-hitter, Wes Helms, struck out, and the crowd filled with Phillies fans simply began to roar.

From there, it was all up to Paulino, who fouled the first pitch into the seats along the first-base side, took ball one, swung and missed for strike two, and then stabbed at Halladay’s 115th and final offering. Castro ranged to his left to get it and threw across to first baseman Ryan Howard, who caught the ball and jumped in the air.

In a week that saw the hard-hitting Phillies get shut out on three straight days by the New York Mets, Halladay delivered the most masterful pitching performance of all.

“He did what he had to do,” Phillies manager Charlie Manuel said. “We gave him one run. He made it stand up. That was good. Super for him.”

On the short list of baseball’s perfect games, there are the first two: John Richmond and John Ward pitched them five days apart in 1880, two decades before what is considered the modern era.