Prado\Web\UI\WebControls\TWizard::getPreviousStepIndex PHP Method

    protected function getPreviousStepIndex($popStack)
    {
        $history = $this->getHistory();
        if ($history->getCount() >= 0) {
            $activeStepIndex = $this->getActiveStepIndex();
            $previousStepIndex = -1;
            if ($popStack) {
                $previousStepIndex = $history->pop();
                if ($activeStepIndex === $previousStepIndex && $history->getCount() > 0) {
                    $previousStepIndex = $history->pop();
                }
            } else {
                $previousStepIndex = $history->peek();
                if ($activeStepIndex === $previousStepIndex && $history->getCount() > 1) {
                    $saveIndex = $history->pop();
                    $previousStepIndex = $history->peek();
                    $history->push($saveIndex);
                }
            }
            return $activeStepIndex === $previousStepIndex ? -1 : $previousStepIndex;
        } else {
            return -1;
        }
    }