The home side took the lead in the 26th minute when Kelyn Rowe picked up the ball 25 yards from goal and drilled a shot into the bottom corner of the net.
After the break, the Union drew level with a lovely move which was ended when Conor Casey found Danny Cruz in the penalty area and he slotted the ball home.
New England responded immediately and regained the lead through an own goal from Philadelphia defender Amobi Okugo as he sliced the ball into his own net from an effort from Juan Agudelo.
Rowe made it three, with his second of the game, with another fine effort from distance which beat the outstretched hand of Union keeper Zac MacMath.
Diego Fagundez added to the Union's misery when he latched onto Scott Caldwell's through-ball and dispatched an effort past MacMath, while minutes later Agudelo made it five with a lovely clipped finish.
Philadelphia finished the game with 10 men when Okugo was sent off for a second bookable offence, as New England cantered to a comfortable win.