Updated

HOUSTON (Reuters) - Roy Halladay pitched his first shutout of the season as the Philadelphia Phillies beat the Houston Astros 1-0 on Wednesday to become the first team to book a place in the Major League Baseball playoffs.

Halladay (18-5) finished with seven strikeouts and one walk to help the National League East-leading Phillies snap a three-game losing streak.

The Phillies needed either a win against the Astros or a St. Louis Cardinals loss on Wednesday to secure a playoff spot. The Cardinals ended up beating the Pirates 3-2.

"Roy did a heck of a job," Phillies manager Charlie Manuel told reporters. "He had good command, especially (against) the young hitters. He threw them a lot of off-speed stuff. He didn't throw them a lot of fastballs that they could get to.

"Where he's putting the ball is what really counts, but that comes with a lot of preparation and he's always ready."

Two-time Cy Young Award winner Halladay was delighted to help his team clinch a playoff berth.

"That's the reason you're here," he said after recording the 66th complete game of his career, and his eighth this season. "We expect to win, and you get converted to that quickly. It's a great mentality to have.

"Obviously there's some work that we want to get done -- trying to win the division and get ourselves home field -- but going to the playoffs is always a thrill. That's the ultimate reason you're playing the game."

Shane Victorino led off with a double in the first inning and scored the only run on a Placido Polanco single to put Philadelphia in control.

Houston starter Bud Norris (6-10) retired the next 15 batters before the Phillies came close to scoring again in the sixth inning.

Halladay led off with a single but, after a walk to Victorino, was forced out on a Polanco grounder. Though Hunter Pence singled to load the bases, the Phillies failed to take advantage as Ryan Howard struck out and Raul Ibanez flied out.

The Phillies (95-51) increased their lead in the National League East division to 11 games over the second-placed Atlanta Braves.

(Writing by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)