/**
  * read_all_entries get all inventory-entries from db for that the actual
  * user has sufficient rights. returns an array with inventory-objects
  * 
  * @param bool $all all the user has rights to, if true, only owned, if false
  * @return array all entries as inventory-objects
  */
 private function read_all_entries($all = false)
 {
     // prepare return
     $inventory_entries = array();
     // get ids
     if (!$all) {
         $inventory_ids = Inventory::return_my_inventories();
     } else {
         $inventory_ids = Inventory::return_inventories();
     }
     // create inventory-objects
     foreach ($inventory_ids as $index => $id) {
         $inventory_entries[] = new Inventory($id);
     }
     // return calendar-objects
     return $inventory_entries;
 }