Contao\DC_Folder::ajaxTreeView PHP Method

    public function ajaxTreeView($strFolder, $level)
    {
        if (!\Environment::get('isAjaxRequest')) {
            return '';
        }
        /** @var SessionInterface $objSession */
        $objSession = \System::getContainer()->get('session');
        $blnClipboard = false;
        $arrClipboard = $objSession->get('CLIPBOARD');
        // Check clipboard
        if (!empty($arrClipboard[$this->strTable])) {
            $blnClipboard = true;
            $arrClipboard = $arrClipboard[$this->strTable];
        }
        $blnProtected = true;
        $strPath = $strFolder;
        // Check for public parent folders (see #213)
        while ($strPath != '' && $strPath != '.') {
            if (file_exists(TL_ROOT . '/' . $strPath . '/.public')) {
                $blnProtected = false;
                break;
            }
            $strPath = dirname($strPath);
        }
        $this->import('Files');
        $this->import('BackendUser', 'User');
        return $this->generateTree(TL_ROOT . '/' . $strFolder, $level * 20, false, $blnProtected, $blnClipboard ? $arrClipboard : false);
    }