Bits with the prefix "J" and "PH" are often thought to be the same bit. Don't be fooled by their similar appearance—they are quite different.
Phillips (PH) screws are designed to make a Phillips screwdriver cam out if too much torque is applied. This prevents damage to screws and screwdrivers or bits.
Japanese Industrial Standard (J) screws do not provide a cam-out option, and have 90 degree corners.