[=WoR=G4M3Ov3r]

PHP код:

stock IsValidName(playerid)
{
    if (IsPlayerConnected(playerid))
    {
        new player[24];
        GetPlayerName(playerid,player,24);
        for(new n = 0; n < strlen(player); n++)
        {
            if (player[n] == '_') return 1;
            if (player[n] == ']' || player[n] == '[') return 0;
        }
    }
    return 0;
} 


There you go