OnInvionAskForHelp;...

[AzTeC]

Code:

public OnPlayerConnect(playerid)
{
    new pName[MAX_PLAYER_NAME];
    new string[48];
   
    GetPlayerName(playerid, pName, sizeof(pName));
   
    format(string, sizeof(string), "%s has joined the server.", pName);
    SendClientMessageToAll(0xAAAAAAAA, string);
    return 1;
}

this should work