The PGA Championship cut line is determined by reducing the 156-player field down significantly heading into the final two rounds.
The PGA Championship cut rule is similar to what you'll see week to week on the PGA Tour, with the top 70 players and ties getting into the final two rounds. There is no 10-shot rule, which means there's no guarantee that a player within 10 shots of the lead qualifies for the weekend rounds. There is a 10-shot rule at the Masters.
There's also no secondary cut if 78 or more professionals make the cut, as would be the case in a standard PGA Tour event.
The cut line is hovering between 1 over par and 2 over par, with the 20 PGA of America club professionals subject to the same cut as the other players in the field.