[RogueDrifter]

._. do a variable check that checks true onplayerspawn and false onplayerdisconnect? ex:

PHP код:

new bool:OneMessage[MAX_PLAYERS];
public OnPlayerSpawn(playerid)
{
    if(!OneMessage[playerid])//checking if it was never set before
    {
        SendClientMessage(playerid, -1, "Hi one message here");//sending the message
        OneMessage[playerid] = true;//checking true to make it get called once
        }
    return 1;
}
public OnPlayerDisconnect(playerid, reason)
{
    OneMessage[playerid] = false;// resetting it for the next player connecting with that id.
    return 1;
}