IsPlayerInArea(playerid, Float:MinX, Float:MinY, Float:MaxX, Float:MaxY)
{
    new Float:X, Float:Y, Float:Z;

    GetPlayerPos(playerid, X, Y, Z);
    if(X >= MinX && X <= MaxX && Y >= MinY && Y <= MaxY) {
        return 1;
    }
    return 0;
}

public OnPlayerUpdate(playerid)
{
   if(IsPlayerInArea(playerid, 0.0, 0.0,0.0,0.0))
      {
          SetPlayerHealth(playerid,0);
       }
    return 1;
}