new pRank[MAX_PLAYERS]; //A rank variable for players.

public OnPlayerConnect(playerid)
{
 pRank[playerid] = 0; //Set it to 0 or else the previous player's rank will be for the new connected player too.
 return 1;
}

CMD:setrank(playerid, params[])
{
 //You can split the parameters using sscanf2. Check out the sscanf2 tutorials for more info about it.
 if(!IsPlayerAdmin(playerid)) return SendClientMessage(playerid, -1, "You need to login as RCON admin to use this command!"); //To ensure that admins can only use it, else you can uncomment this line or replace with your variables.
 new p2, rank;
 if(sscanf(params, "ri", p2, rank)) return SendClientMessage(playerid, -1, "Usage: /setrank [playerid] [rank]");
 if(p2 == INVALID_PLAYER_ID) return SendClientMessage(playerid, -1, "This player ID is not VALID!");
 if(!IsPlayerConnected(p2)) return SendClientMessage(playerid, -1, "This player is not connected!");
 if(rank > 7 || rank < 0) return SendClientMessage(playerid, -1, "Invalid rank. Ranks from 1 - 7 only!"); //if rank > 7 (rank is greater than 7) or if rank < 0 (rank is lesser than 0); then it messages that it's not valid rank!
 if(rank == pRank[p2]) return SendClientMessage(playerid, -1, "Player is already in this rank!"); //If rank is the same value of other player's rank, it will send as it's already the other's rank.
 //In case of messages / notifications:
 new string[128];
 format(string, sizeof(string), "%s (ID: %d) has set your rank to %d", ReturnName(playerid), playerid, rank);
 SendClientMessage(p2, -1, string);
 format(string, sizeof(string), "You have set %s's (ID: %d) rank to %d", ReturnName(p2), p2, rank);
 SendClientMessage(playerid, -1, string);
 pRank[p2] = rank; //Sets the rank here!
 return 1; //Returns the command.
}

CMD:memberlist(playerid, params[])
{
 new string[128];
 SendClientMessage(playerid, -1, "=================User rankings==================");
 for(new i; i< GetMaxPlayers(); i++)
 {
  if(!IsPlayerConnected(i)) continue;
  if(pRank[i] >= 1)
  {
   format(string, sizeof(string), "%s (ID:%d) - Rank: %d\n", ReturnName(i), i, pRank[i]);
   SendClientMessage(playerid, -1, string);
  }
 }
 return 1;
}

stock ReturnName(playerid)
{
 new Lname[MAX_PLAYER_NAME];
 GetPlayerName(playerid, Lname, sizeof(Lname));
 return Lname;
}