SAN FRANCISCO -- Brandon Belt cleared the bases with a three-run double in a four-run seventh inning Friday night, rallying the San Francisco Giants from a deficit and into a 5-4 victory over the Philadelphia Phillies in the opener of a three-game series.

Right-hander Jake Peavy limited the Phillies to two runs in seven innings for his second consecutive win as the Giants won for the 12th time in their last 13 games overall and 12th time in their last 14 home dates.

The win was the Giants' 31st in their last 40 games, the club's best 40-game run since also going 31-9 from June 12-July 21, 1954.

Phillies rookie right-hander Zach Eflin pitched six strong innings in his third major league start and left with a 2-1 lead before the Giants erupted against the Philadelphia bullpen.

Trevor Brown greeted right-hander Severino Gonzalez with a single to lead off the seventh, prompting Phillies manager Pete Mackanin to switch to lefty Elvis Araujo (1-1).

A single by pinch-hitter Buster Posey and one-out walk to Joe Panik loaded the bases for Belt, whose towering blast to the deepest part of the ballpark in right-center field landed on the warning track for a double, easily allowing all three Giants baserunners to score and produce a 4-2 lead.

Angel Pagan's two-out single scored Belt with the inning's fourth run, increasing the lead to 5-2.

The Phillies got within 5-4 in the eighth on Freddy Galvis' two-out RBI single and a bases-loaded walk to Peter Bourjos. But right-hander Cory Gearrin, the fourth Giants pitcher, retired pinch-hitter Andres Blanco on a grounder to first to strand three baserunners.

Lefty Javier Lopez and closer Santiago Casilla combined on a one-hit ninth to close out the Giants' 18th one-run win of the season. Casilla got the final two outs for his 17th save, finishing off the Phillies by inducing Tyler Goeddel to ground to third with the bases loaded.

The final out, a close play at first base, was reviewed and confirmed.

Peavy (4-6), who began the season 1-5, won for the third time in his last five starts. He allowed seven hits and two walks in his seven innings, striking out four.

The seven-inning effort matched the 35-year-old's longest of the season.

Giants starters have gone 8-0 with a 1.75 ERA in the team's last 14 home games.

Pagan had three hits and drove in two runs for the Giants (48-27), who improved to a season-best 21 games over .500 in the opener of a five-game homestand.

Belt had two doubles among the Giants' nine hits.

Franco, Cameron Rupp, Galvis and Bourjos had two hits apiece for the Phillies, who have lost 13 of their last 16 games against the Giants.

One day after recording a season-best eight extra-base hits at Minnesota, the Phillies banged out six more, with Franco producing a double and a triple.

Eflin limited the Giants to five hits and an unearned run in his six innings. The 22-year-old struck out one and did not walk a batter.

The Phillies have lost 10 of their last 11.

The Phillies' first four hits off Peavy were all doubles, the last three contributing to a pair of runs that allowed the visitors to overcome an early 1-0 deficit.

Philadelphia drew even in the fourth when Maikel Franco and Ryan Howard hit back-to-back, one-out doubles.

Odubel Herrera's sacrifice fly scored Freddy Galvis, who had led off the fifth inning with a double, to put the Phillies in front 2-1.

The Giants opened the game's scoring in the bottom of the first after leadoff man Denard Span reached on an error by Howard, the Phillies' first baseman.

Span scored on Angel Pagan's two-out infield single.

NOTES: The Giants (47-27) began the night tied with the Chicago Cubs (47-24) and Texas Rangers (47-26) for the most wins in the majors. ... The Phillies haven't won a series since taking two of three from the Miami Marlins on May 16-18. ... Phillies RHP Vincent Velasquez (strained right bicep) joined the team in San Francisco on Friday. He is eligible to be reinstated from the 15-day disabled list and is a candidate to rejoin the starting rotation next week in Arizona. ... Before the game, the Phillies placed RHP Andrew Bailey (strained left hamstring) on the 15-day DL and promoted RHP Edubray Ramos from Triple-A Lehigh Valley. ... Giants RHP Sergio Romo (strained right flexor) returned to the parent club Friday after a four-game injury-rehab stint in the minors. A decision on whether to activate him from the DL will be made over the weekend.