source: extensions/language_switch_menubar/main.inc.php

<?php
/*
Plugin Name: Language Switch Menubar
Version: auto
Description: Switch to another language from flags on your menubar gallery.
Plugin URI: http://piwigo.org/ext/extension_view.php?eid=601
Author: ddtddt
Author URI: http://temmii.com/piwigo/
*/

// +-----------------------------------------------------------------------+
// | Language Switch Menubar plugin for piwigo by TEMMII                   |
// +-----------------------------------------------------------------------+
// | Copyright(C) 2012-2021 ddtddt               http://temmii.com/piwigo/ |
// +-----------------------------------------------------------------------+
// | This program is free software; you can redistribute it and/or modify  |
// | it under the terms of the GNU General Public License as published by  |
// | the Free Software Foundation                                          |
// |                                                                       |
// | 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      |
// | General Public License for more details.                              |
// |                                                                       |
// | You should have received a copy of the GNU General Public License     |
// | along with this program; if not, write to the Free Software           |
// | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, |
// | USA.                                                                  |
// +-----------------------------------------------------------------------+

if (!defined('PHPWG_ROOT_PATH'))
{
  die('Hacking attempt!');
}

define('LSM_DIR' , basename(dirname(__FILE__)));
define('LSM_PATH' , PHPWG_PLUGINS_PATH . LSM_DIR . '/');

add_event_handler('blockmanager_register_blocks', 'register_lsm_menubar_blocks');
add_event_handler('blockmanager_apply', 'lsm_apply');
add_event_handler('loading_lang', 'reloadlang');

function register_lsm_menubar_blocks( $menu_ref_arr )
{
  $menu = & $menu_ref_arr[0];
  if ($menu->get_id() != 'menubar')
    return;
  $menu->register_block( new RegisteredBlock( 'mbLSM', 'lsm', 'LSM'));
}

function lsm_apply($menu_ref_arr)
{
  global $template, $user, $template, $conf, $page;

  $menu = & $menu_ref_arr[0];
 
  load_language('plugin.lang', LSM_PATH);
        $template->assign(
    array       (
      'LSMTITLE' => l10n('Language'),
      )
    );
 
  if (($block = $menu->get_block( 'mbLSM' )) != null)
  {
    $template->set_template_dir(LSM_PATH.'template/');
        if ($user['theme'] == 'bootstrapdefault'||$user['theme'] == 'bootstrap_darkroom'){
          $block->template = 'flags_bootstrap.tpl';     
        }else if ($user['theme'] == 'smartpocket'){
          $block->template = 'flags_smartpocket.tpl';           
        }else{
          $block->template = 'flags.tpl';
        }
  }
  
  if (isset($page['section']) and $page['section'] == 'additional_page' and isset($page['additional_page']))
  {
    $base_url = make_index_url(array('section'=>'page')).'/'.(isset($page['additional_page']['permalink']) ? $page['additional_page']['permalink'] : $page['additional_page']['id']);
  }
  else
  {
    $base_url = duplicate_index_url();
  }
 
  $available_lang = get_languages();
  foreach ($available_lang as $code => $displayname)
  {
        $code2=explode("_", $code);
    $qlc = array (
      'url' => add_url_params($base_url, array('lang'=> $code)),
      'alt' => ucwords($displayname),
          'hreflang' =>$code2[0],
      'img' => get_root_url().'language/'.$code.'/'.$code.'.jpg',
      );
    
    $lsw['flags'][$code] = $qlc ;
    
    if ($code == $user['language'])
    {
      $lsw['Active'] = $qlc;
    }
  }

  $lsw['side'] = ceil(sqrt(count($available_lang)));
  $template->clear_assign('lang_switch');   
  $template->assign(
    array(
      'lang_switch'=> $lsw,
      'LSM_PATH' => LSM_PATH,
      )
    );
}

function reloadlang()
{
  global $user;
  $same = $user['language'];   
 
  if (isset($_GET['lang']))
  {
    if (!empty($_GET['lang']) and file_exists(PHPWG_ROOT_PATH.'language/'.$_GET['lang'].'/common.lang.php'))
    {
      if (is_a_guest() or is_generic())
      {
        pwg_set_session_var('lang_switch', $_GET['lang']);
      }
      else
      {
        $query = '
UPDATE '.USER_INFOS_TABLE.'
  SET language = \''.$_GET['lang'].'\'
  WHERE user_id = '.$user['id'].'
;';
        pwg_query($query);
      }
      $user['language'] = $_GET['lang'];
    }
  }
  elseif ((is_a_guest() or is_generic()))
  {
    $user['language'] = pwg_get_session_var('lang_switch', $user['language']);
  }
  
  if ( $same !== $user['language'])
  {
    load_language('common.lang', '', array('language'=>$user['language']));
    
    load_language(
      'lang',
      PHPWG_ROOT_PATH.PWG_LOCAL_DIR,
      array(
        'language' => $user['language'],
        'no_fallback' => true,
        'local' => true
        )
      );
  }
    
  if (defined('IN_ADMIN') and IN_ADMIN)
  {
    load_language('admin.lang', '', array('language'=>$user['language']));
  }
}

?>