class steam {
        function __construct(){
            $this->OnLoginCallback = function(){};
        }

        function Init(){
            if($this->IsUserLoggedIn()){
                $this->SteamID = $_SESSION['steamid'];
                return;
            }

            if($this->OpenID->mode){
                if($this->OpenID->validate()){
                    $this->SteamID = basename($this->OpenID->identity);
                    if($this->OnLoginCallback($this->SteamID)){
                        $_SESSION['steamid'] = $this->SteamID;
                    }
                }
            }
        }

        function SetOnLoginCallback($callback){
            $this->OnLoginCallback = $callback;
        }
   }

$steam->SetOnLoginCallback(function($steamid64){
    return true;
});

$steam->Init();