[Sinner]

PHP код:

dcmd_addtag(playerid, params[])
{
    new player, tagname[20];
    if(sscanf(params, "us", player, tagname)) return SendClientMessage(playerid, 0xFFFFFF, "USAGE: /Addtag [playerid] [tag]");
    new str[MAX_NAME_LEN], name[MAX_NAME_LEN];
    GetPlayerName(player, name, sizeof(name));
    format(str, sizeof(str), "[%s]%s", tagname, name);
    SetPlayerName(player, str);
} 


For example, "/addtag 5 owner"
This requires sscanf and dcmd