Do some serverside verification.
PHP Code:
function onActionServerSide() {
if (params[0] == "addclass") {
if (clientr.class != null) {
return player.chat = "You already have a class!";
}
temp.validClasses = {"Archer", "Wizard", "Knight", "etc"};
if (! (params[1] in temp.validClasses)) {
return player.chat = "That's not a valid class!";
}
clientr.class = params[1]; //Adds the player flag
}
}