[RogueDrifter]

PHP код:

new bool:afkcheck[MAX_PLAYERS];// on top of the script (creating a variable to check for on/off stats)
CMD:afk(playerid, params[])//afk cmd
{
    if(!afkcheck[playerid])//checking if he's not afk (!)
     {
        new name[MAX_PLAYER_NAME], string[40];
        GetPlayerName(playerid, name, MAX_PLAYER_NAME);
        format(string, sizeof(string), "%s Is Now Afk.", name);
        SCMTA(0xFFFF00, string);
        TogglePlayerControllable(playerid, 0);
        afkcheck[playerid]=true;//making the check count true when enabling afk
        }
    else//if he's already afk
     {
     SendClientMessage(playerid,-1,"You're already afk!");
     }
    return 1;
}
//==============================================================================
CMD:back(playerid, params[])//back cmd
{
    if(afkcheck[playerid])//checking if he's afk 
     {
        new name[MAX_PLAYER_NAME], string[40];
        GetPlayerName(playerid, name, MAX_PLAYER_NAME);
        format(string, sizeof(string), "%s back from Afk.", name);
        SCMTA(0xFFFF00, string);
        TogglePlayerControllable(playerid, true);
        afkcheck[playerid]=false;//making the variable count as false when he comes back from afk
        }
     else//if he isn't afk
     {
         SendClientMessage(playerid,-1,"You're not afk!");
         }
return 1;
} 


but don't forget to put afkcheck[playerid]=false; underneath OnPlayerSpawn in case if a player logs out while afk.