Per MMQB:
"...One more note about this: After the play, Twitter was filled with people saying the Eagles were short one man on the line of scrimmage at the snap of the ball. The NFL requires seven offensive players to be on the line of scrimmage before the ball is snapped. And it does appear that six Eagles were within a yard of the line, which is permissible, and the seventh, wide receiver Alshon Jeffery, to the top of the formation, was two yards off the line. In theory, the officials could have called an illegal formation with only six men on the line.
Except Jeffery claimed he got the okay from the official on the right sideline. The way formation rules work, players can look over at a side judge or other official nearby to see if he’s in the permissible spot.
“I’m on the ball,” Jeffery said. “I pointed. What are you talking about? Man, you know I checked with the ref!”