Before forging ahead, I'd like a disclaimer. I don't claim this tutorial to be uniquely mine, it's an amalgamation of techniques from several pages and sites. Neither is it the most comprehensive and in-depth guide.

That said, I certainly hope after using this guide you can quickly and easily implement multiple languages in your cake app without needing to skip around the place. If I fall short of this and you have suggestions, leave a comment.

Once you complete this tutorial your site will be able to:

1. display multiple languages
2. allow users to switch languages
3. store language settings in cookies, so returning visitors don't need to re-select their preferred language

The sites that I build typically require 3 languages:

1. British English(en-gb)
2. Simplified Chinese(zh-cn)
3. Traditional Chinese(zh-tw)

So throughout this document, I'll be using them as my reference languages. Your site may support more or less languages.

Step 1: Setup the directories for your messages

$ cd cake/app/locale/

$ mkdir en_gb

$ mkdir en_gb/LC_MESSAGES

$ mkdir zh_tw

$ mkdir zh_tw/LC_MESSAGES

$ mkdir zh_cn

$ mkdir zh_cn/LC_MESSAGES

This will create the minimum folders required for each language our site needs to support.

To find your language code(s) refer to http://api.cakephp.org/1.2/l10n_8php-source.html#l00180 //this is only a sample. don't add this to your code.
'nl' => array(
    'language' => 'Dutch (Standard)', 
    'locale' => 'dut', 
    'localeFallback' => 'dut', 
    'charset' => 'utf-8'
),
'pl' => array(
    'language' => 'Polish', 
    'locale' => 'pol', 
    'localeFallback' => 'pol', 
    'charset' => 'utf-8'
),
'sk' => array(
    'language' => 'Slovack', 
    'locale' => 'slo', 
    'localeFallback' => 'slo', 
    'charset' => 'utf-8'
),
By studying the sample above, we can see that directory names are actually the locale:

• 'dut' is the correct directory name(locale) for 'nl'
• 'pol' is the correct directory name(locale) for 'pl'
• 'slo' is the correct directory name(locale) for 'sk'

Step 2: Write some strings to translate.

View Template:

<?php $this->pageTitle = __('pageTitle_home', true); ?>

<h1><?php __('welcome_heading'); ?></h1>
<?php __('lipsum'); ?><?php __('lipsum'); ?><?php __('lipsum'); ?><br/>
<?php __('lipsum'); ?><?php __('lipsum'); ?><?php __('lipsum'); ?><br/>
<?php __('footer_copyright'); ?>
note: The 2nd parameter controls whether a message should be returned or echo'd
So when you are working with a template, use:

PHP Snippet:

<?php __('my_name');?> And when you are working with code, use:

PHP Snippet:

<?php $name = __('my_name', true);?>

Step 3: Let's build a database from our PHP and templates.

$ cd cake/app/

$ cake extract

This will recursively go through all the folders and check both your .php and .ctp files for all of those __() functions you typed. Once it's complete, you should have a nice message template file named default.pot file inside cake/app/locale/

So let's copy this message template file into the right directories for each language.

$ cd cake/app/locale/

$ cp default.pot locale/en_gb/LC_MESSAGES/default.po

$ cp default.pot locale/zh_tw/LC_MESSAGES/default.po

$ cp default.pot locale/zh_cn/LC_MESSAGES/default.po

note: at this point in time, you can freely edit the default.po files(they're just text) and start translating strings. Changes made to these files will automatically be rendered in your views.

Here are some short snippets from my default.po files.

// locale/zh_cn/LC_MESSAGES/default.po
msgid "footer_copyright"
msgstr "教育局 © 2007. 版权所有"

// locale/zh_tw/LC_MESSAGES/default.po
msgid "footer_copyright"
msgstr "教育局 © 2007. 版權所有"

// locale/en_gb/LC_MESSAGES/default.po
msgid "footer_copyright"
msgstr "Education Bureau © 2007. All rights reserved."


Step 4: Change the default language

A fresh install of cakePHP is set to use American English, so for the rest of us: we need that changed.
// config/bootstrap.php
define(DEFAULT_LANGUAGE, 'zh-tw');


Step 5: Let users change the language

Component Class:

<?php 
class P28nComponent extends Object {
    var $components = array('Session', 'Cookie');

    function startup() {
        if (!$this->Session->check('Config.language')) {
            $this->change(($this->Cookie->read('lang') ? $this->Cookie->read('lang') : DEFAULT_LANGUAGE));
        }
    }

    function change($lang = null) {
        if (!empty($lang)) {
            $this->Session->write('Config.language', $lang);
            $this->Cookie->write('lang', $lang, null, '+350 day'); 
        }
    }
}
?> _{Thanks Nasko for pointing out that Cookie->write() does not accept timestamps}

Controller Class:

<?php 
class P28nController extends AppController {
    var $name = 'P28n';
    var $uses = null;
    var $components = array('P28n');

    function change($lang = null) {
        $this->P28n->change($lang);

        $this->redirect($this->referer(null, true));
    }

    function shuntRequest() {
        $this->P28n->change($this->params['lang']);

        $args = func_get_args();
        $this->redirect("/" . implode("/", $args));
    }
}
?>

Controller Class:

<?php 
//app_controller.php
class AppController extends Controller {
    var $components = array('P28n');
}
?> The final piece of code, are some custom routes that need to be added to cake/app/config/routes.php
<?php
//route to switch locale
Router::connect('/lang/*', array('controller' => 'p28n', 'action' => 'change'));

//forgiving routes that allow users to change the lang of any page
Router::connect('/eng?/*', array(
    'controller' => "p28n",
    'action' => "shuntRequest",
    'lang' => 'en-gb'
));

Router::connect('/zh[_-]tw/*', array(
    'controller' => "p28n",
    'action' => "shuntRequest",
    'lang' => 'zh-tw'
));

Router::connect('/zh[_-]cn/*', array(
    'controller' => "p28n",
    'action' => "shuntRequest",
    'lang' => 'zh-cn'
));
?>


Step 6: Links to change language

View Template:

<h1><?php __('welcome_heading'); ?></h1>
<?php __('lipsum'); ?><?php __('lipsum'); ?><?php __('lipsum'); ?><br/>
<?php __('lipsum'); ?><?php __('lipsum'); ?><?php __('lipsum'); ?><br/>
<?php __('footer_copyright'); ?>

<!-- these links will change the language, but allow the user to stay on this page //-->
<?php echo $html->link($html->image('en_gb.gif'), '/lang/en-gb', null, null, false); ?>
<?php echo $html->link($html->image('zh_tw.gif'), '/lang/zh-tw', null, null, false); ?>
<?php echo $html->link($html->image('zh_cn.gif'), '/lang/zh-cn', null, null, false); ?>

<!-- these links will change the language, then forward the user to the /news page //-->
<?php echo $html->link($html->image('en_gb.gif'), '/en-gb/news', null, null, false); ?>
<?php echo $html->link($html->image('zh_tw.gif'), '/zh-tw/news', null, null, false); ?>
<?php echo $html->link($html->image('zh_cn.gif'), '/zh-cn/news', null, null, false); ?>


Step 7: All done.

Assuming I have included all the right code and not forgotten anything, you should now be fully functional^^

Further reading

A popular cross-platform GUI tool for managing .po files is poEdit http://www.poedit.net/ Gettext and cakePHP supports much more than word for word, literal translations. Check out __(), __c(), __d(), __dc(), __dcn(), __dn(), __n() http://api.cakephp.org/1.2/basics_8php.html
..and finally, remember that utf-8 is your friend. treat it well, and it'll reciprocate.