PHILADELPHIA — Pennsylvania’s gross slot machine revenue was up 3.4 percent in May over the year before, boosted by the second full month of play at Valley Forge Casino Resort in suburban Philadelphia. Existing casinos, meanwhile, saw a modest rise.

The state’s 11 casinos — including Valley Forge, which opened March 31 — collected $212.5 million in gross slots revenue in May, an increase over $205.5 million from the same period the year before, according to revenue figures released Monday by the Pennsylvania Gaming Control Board. The 10 existing casinos that were open in both May 2011 and May 2012 saw an increase of 1.5 percent in May, a month after their gross slots revenue had dipped .6 percent.

Sands Casino Resort Bethlehem showed the most growth in May, pulling in $25.1 million in gross slots revenue, an increase of 11.2 percent over May 2011. The state’s second-newest facility, Sugarhouse Casino in Philadelphia, wasn’t far behind: It reported $16.4 million in gross revenue, an increase of just less than 10 percent.

Presque Isle Downs Casino in Erie showed the biggest loss in May, a 10.6 percent decrease to $13 million.

In March, the state’s casinos set an all-time monthly high with $233.1 million in gross revenue, the most for a period since Pennsylvania’s first casino opened in November 2006. Pennsylvania recently passed Atlantic City as the nation’s second-largest gambling market behind Las Vegas.

The state taxes casino revenue and uses it to support the state budget, public schools, civic development projects, volunteer firefighting squads, local governments and the horse racing industry.