new Float:x, Float:y, Float:z;

GetPlayerPos(playerid, x, y, z);
SetPlayerPos(playerid, x, y, z+1);

forward GetPosFrontOfPlayer(playerid, Float:OffDist, &Float:Pxx, &Float:Pyy, &Float:Pzz);
public GetPosFrontOfPlayer(playerid, Float:OffDist, &Float:Pxx, &Float:Pyy, &Float:Pzz)
{
/*******************************************************************************
  Function: GetPosFaInFrontOfPlayer
  Parameter:
    playerid - the player on wich the output pos will be based on
    OffDist - The distance that the X Y point will be from playerid
    Pxx - Val to put x in
    Pyy - Val to put y in
    Pzz - Val to put z in
  Return:
    1 - Sucess
    0 - playerid was not connected
*******************************************************************************/
  if(!IsPlayerConnected(playerid)) return 0;
  new
    Float:playerpos[3],
        Vid,
    Float:FacingA;
  Vid = GetPlayerVehicleID(playerid);
    if(!Vid) //player not in a vehicle
  {
    GetPlayerPos(playerid, playerpos[0], playerpos[1], playerpos[2]);
    GetPlayerFacingAngle(playerid, FacingA);
  }
  else // player is in a vehicle
  {
    GetVehiclePos(Vid, playerpos[0], playerpos[1], playerpos[2]);
    GetVehicleZAngle(Vid, FacingA);
  }
  Pxx = (playerpos[0] + OffDist * floatsin(-FacingA,degrees));
  Pyy = (playerpos[1] + OffDist * floatcos(-FacingA,degrees));
  Pzz = playerpos[2];
  return 1;
}

GetPlayerPos(playerid,x,y,z);
AttachObjectToPlayer(objectid,x,y,z+1);