// Somewhere in your script
new NameTag[MAX_PLAYERS];


if (strcmp("/nameoff", cmdtext, true) == 0)
{
    for(new i = 0; i < MAX_PLAYERS; i++)
        ShowPlayerNameTagForPlayer(i, playerid, false);
        
    NameTag[playerid] = 0;
    GameTextForPlayer(playerid, "~W~Nametags ~R~off", 5000, 5);
    return 1;
}
if (strcmp("/nameon", cmdtext, true) == 0)
{
    for(new i = 0; i < MAX_PLAYERS; i++)
        ShowPlayerNameTagForPlayer(i, playerid, true);
        
    NameTag[playerid] = 1;
    GameTextForPlayer(playerid, "~W~Nametags ~G~ON", 5000, 5);
    return 1;
}

public OnPlayerConnect(playerid)
{
    NameTag[playerid] = 1;
    for(new i = 0; i < MAX_PLAYERS; i++)
        if(NameTag[i] == 0)
            ShowPlayerNameTagForPlayer(playerid, i, false);

    return 1;
}