Code:
CMD:id(playerid, params[])
{
new target_id, string[256], target_name[MAX_PLAYER_NAME 1];
if (sscanf(params, "u", target_id)) return SendClientMessage(playerid, -1, "USAGE: /id <nick/playerid>");
GetPlayerName(target_id, target_name, sizeof(target_name));
format(string, sizeof(string), "%s [ID: %d]", target_name, target_id)
SendClientMessage(playerid, -1, string);
return 1;
}