-echo sqimap_mailbox_option_list($imapConnection, $show_selected, $skip_folders, $boxes, 'noinferiors');
+// Call sqimap_mailbox_option_list, using existing connection to IMAP server,
+// the arrays of folders to include or skip (assembled above),
+// use 'noinferiors' as a mailbox filter to leave out folders that can not contain other folders.
+// use the long format to show subfolders in an intelligible way if parent is missing (special folder)
+echo sqimap_mailbox_option_list($imapConnection, $show_selected, $skip_folders, $boxes, 'noinferiors', true);