Shadow force and Phantom force are two different attacks.
Phantom Force causes the user to disappear on the first turn, becoming invulnerable to most attacks. On the second turn, it deals damage and can hit Pokemon using Protect or Detect.
The user of Shadow Force will vanish instantly on the first turn, disappearing from view and becoming invulnerable to most attacks. On the second turn, Shadow Force deals damage and can hit Pokemon using Protect or Detect. It also removes their effect for the rest of the turn (in double and triple battles).
While disappeared, the Pokemon can only be hit by moves from No Guard Pokemon, or any move following an identify move.
If the user is holding a Power Herb, Shadow Force executes in one turn.
Hope I helped :D