[Anteino]

pawn Код:

new Registered[MAX_PLAYERS] // should be globally declared
...
new File[50];
    format(File, sizeof(File), PFiles, pName(playerid));

    if(fexist(File)){
Registered[playerid] = 1;
...

public OnPlayerRequestClass(playerid, classid){
if(Registered[playerid] == 1){
return 1;
}
else{
// the class thing
}
return 1;
}

public OnPlayerDisconnect(playerid){
Registered[playerid] = 0;
}

Isn't that what you want?