diff --git a/lib/api/common.php b/lib/api/common.php
index 5cb0896..858008e 100644
--- a/lib/api/common.php
+++ b/lib/api/common.php
@@ -1,272 +1,271 @@
 <?php
 /*
  +--------------------------------------------------------------------------+
  | This file is part of the Kolab File API                                  |
  |                                                                          |
  | Copyright (C) 2012-2014, Kolab Systems AG                                |
  |                                                                          |
  | This program is free software: you can redistribute it and/or modify     |
  | it under the terms of the GNU Affero General Public License as published |
  | by the Free Software Foundation, either version 3 of the License, or     |
  | (at your option) any later version.                                      |
  |                                                                          |
  | This program is distributed in the hope that it will be useful,          |
  | but WITHOUT ANY WARRANTY; without even the implied warranty of           |
  | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the             |
  | GNU Affero General Public License for more details.                      |
  |                                                                          |
  | You should have received a copy of the GNU Affero General Public License |
  | along with this program. If not, see <http://www.gnu.org/licenses/>      |
  +--------------------------------------------------------------------------+
  | Author: Aleksander Machniak <machniak@kolabsys.com>                      |
  +--------------------------------------------------------------------------+
 */
 
 class file_api_common
 {
     protected $api;
     protected $rc;
     protected $args = array();
 
 
     public function __construct($api, $args = array())
     {
         $this->rc   = rcube::get_instance();
         $this->api  = $api;
         $this->args = (array) $args;
     }
 
     /**
      * Request handler
      */
     public function handle()
     {
         // GET arguments
         if (!empty($_GET)) {
             foreach (array_keys($_GET) as $key) {
                 $this->args[$key] = &$_GET[$key];
             }
         }
 
         // POST arguments (JSON)
         if ($_SERVER['REQUEST_METHOD'] == 'POST') {
             $post = file_get_contents('php://input');
             $this->args += (array) json_decode($post, true);
             unset($post);
         }
 
         // disable script execution time limit, so we can handle big files
         @set_time_limit(360);
     }
 
     /**
      * File uploads handler
      */
     protected function upload()
     {
         $files = array();
 
         if (is_array($_FILES['file']['tmp_name'])) {
             foreach ($_FILES['file']['tmp_name'] as $i => $filepath) {
                 if ($err = $_FILES['file']['error'][$i]) {
                     if ($err == UPLOAD_ERR_INI_SIZE || $err == UPLOAD_ERR_FORM_SIZE) {
                         $maxsize = ini_get('upload_max_filesize');
                         $maxsize = $this->show_bytes(parse_bytes($maxsize));
 
                         throw new Exception("Maximum file size ($maxsize) exceeded", file_api_core::ERROR_CODE);
                     }
 
                     throw new Exception("File upload failed", file_api_core::ERROR_CODE);
                 }
 
                 $files[] = array(
                     'path' => $filepath,
                     'name' => $_FILES['file']['name'][$i],
                     'size' => filesize($filepath),
                     'type' => rcube_mime::file_content_type($filepath, $_FILES['file']['name'][$i], $_FILES['file']['type']),
                 );
             }
         }
         else if ($_SERVER['REQUEST_METHOD'] == 'POST') {
             // if filesize exceeds post_max_size then $_FILES array is empty,
             if ($maxsize = ini_get('post_max_size')) {
                 $maxsize = $this->show_bytes(parse_bytes($maxsize));
                 throw new Exception("Maximum file size ($maxsize) exceeded", file_api_core::ERROR_CODE);
             }
 
             throw new Exception("File upload failed", file_api_core::ERROR_CODE);
         }
 
         return $files;
     }
 
     /**
      * Return built-in viewer opbject for specified mimetype
      *
      * @return object Viewer object
      */
     protected function find_viewer($mimetype)
     {
         $dir   = RCUBE_INSTALL_PATH . 'lib/viewers';
         $files = array();
 
         // First get viewers and sort by name to get priority
         if ($handle = opendir($dir)) {
             while (false !== ($file = readdir($handle))) {
                 if (preg_match('/^([a-z0-9_]+)\.php$/i', $file, $matches)) {
                     $files[$matches[1]] = $dir . '/' . $file;
                 }
             }
             closedir($handle);
         }
 
         ksort($files);
 
         foreach ($files as $name => $file) {
             include_once $file;
             $class  = 'file_viewer_' . $name;
             $viewer = new $class($this->api);
 
             if ($viewer->supports($mimetype)) {
                 return $viewer;
             }
         }
     }
 
     /**
      * Parse driver metadata information
      */
     protected function parse_metadata($metadata, $default = false)
     {
         if ($default) {
             unset($metadata['form']);
             $metadata['name'] .= ' (' . $this->api->translate('localstorage') . ')';
         }
 
         // localize form labels
         foreach ($metadata['form'] as $key => $val) {
             $label = $this->api->translate('form.' . $val);
             if (strpos($label, 'form.') !== 0) {
                 $metadata['form'][$key] = $label;
             }
         }
 
         return $metadata;
     }
 
     /**
      * Get folder rights
      */
     protected function folder_rights($folder)
     {
         list($driver, $path) = $this->api->get_driver($folder);
 
         $rights = $driver->folder_rights($path);
         $result = array();
         $map    = array(
             file_storage::ACL_READ  => 'read',
             file_storage::ACL_WRITE => 'write',
         );
 
         foreach ($map as $key => $value) {
             if ($rights & $key) {
                 $result[] = $value;
             }
         }
 
         return $result;
     }
 
     /**
      * Collect folder list request parameters
      */
     protected function folder_list_params()
     {
         $params = array('type' => 0);
 
         if (!empty($this->args['unsubscribed']) && rcube_utils::get_boolean((string) $this->args['unsubscribed'])) {
             $params['type'] |= file_storage::FILTER_UNSUBSCRIBED;
         }
 
         if (!empty($this->args['writable']) && rcube_utils::get_boolean((string) $this->args['writable'])) {
             $params['type'] |= file_storage::FILTER_WRITABLE;
         }
 
         if (isset($this->args['search']) && strlen($this->args['search'])) {
             $params['search'] = $this->args['search'];
         }
 
         if (!empty($this->args['permissions']) && rcube_utils::get_boolean((string) $this->args['permissions'])) {
             $params['extended']    = true;
             $params['permissions'] = true;
         }
 
         if (!empty($this->args['level']) && ($level = intval($this->args['level']))) {
             if ($level < 0) {
                 $level *= -1;
                 $params['auto_level'] = true;
             }
 
             $params['level'] = $level;
         }
 
         return $params;
     }
 
     /**
      * Wrapper for folder_list() method on specified driver
      */
     protected function folder_list($driver, $params, $prefix = null)
     {
         $caps = $driver->capabilities();
 
         if ($params['type'] & file_storage::FILTER_UNSUBSCRIBED) {
             if (empty($caps[file_storage::CAPS_SUBSCRIPTIONS])) {
                 return array();
             }
         }
 
         // If the driver has fast way to get the whole folders hierarchy
         // we'll return all folders, despite the requested level, when requested
         if (!empty($params['auto_level']) & !empty($caps[file_storage::CAPS_FAST_FOLDER_LIST])) {
             unset($params['level']);
         }
 
         $folders = $driver->folder_list($params);
-        $plen    = is_string($prefix) ? strlen($prefix) : 0;
 
         if (!empty($folders) && is_string($prefix) && strlen($prefix) > 1) {
             foreach ($folders as $idx => $folder) {
                 if (is_array($folder)) {
-                    $folder[$idx]['folder'] = $prefix . $folder['folder'];
+                    $folders[$idx]['folder'] = $prefix . $folder['folder'];
                 }
                 else {
-                    $folder[$idx] = $prefix . $folder;
+                    $folders[$idx] = $prefix . $folder;
                 }
             }
         }
 
         return $folders;
     }
 
     /**
      * Update document session on file/folder move
      */
     protected function session_uri_update($from, $to, $is_folder = false)
     {
         // check Manticore/WOPI support. Note: we don't use config->get('fileapi_manticore')
         // here as it may be not properly set if backend driver wasn't initialized yet
         $capabilities = $this->api->capabilities(false);
 
         if (!empty($capabilities['WOPI'])) {
             $document = new file_wopi($this->api);
         }
         else if (!empty($capabilities['MANTICORE'])) {
             $document = new file_manticore($this->api);
         }
 
         if (!empty($document)) {
             $document->session_uri_update($from, $to, $is_folder);
         }
     }
 }