[Konstantinos]

I wouldn't use:

pawn Код:

PlayerInfo[playerid][sniper] = "";

but:

pawn Код:

PlayerInfo[playerid][sniper][0] = EOS;
// OR
PlayerInfo[playerid][sniper][0] = '\0';

When you want to make the string empty, use the above instead of "".
Now it's null so:

pawn Код:

new
    count; // it doesn't need to be an array as you said in your above post.

if (!isnull(PlayerInfo[playerid][soldier])) ++count;
if (!isnull(PlayerInfo[playerid][sniper])) ++count;
if (!isnull(PlayerInfo[playerid][assault])) ++count;

// format(...);
// Using "count" as argument will give the total classes.

and

pawn Код:

#if !defined isnull
    #define isnull(%1) \
                ((!(%1[0])) || (((%1[0]) == '\1') && (!(%1[1]))))
#endif

@BroZeus: It's not integer to use "!=".