Chapter 13 - I18n And L10n

If you ever developed an international application, you know that dealing with every aspect of text translation, local standards, and localized content can be a nightmare. Fortunately, symfony natively automates all the aspects of internationalization.

As it is a long word, developers often refer to internationalization as i18n (count the letters in the word to know why). Localization is referred to as l10n. They cover two different aspects of multilingual web applications.

An internationalized application contains several versions of the same content in various languages or formats. For instance, a webmail interface can offer the same service in several languages; only the interface changes.

A localized application contains distinct information according to the country from which it is browsed. Think about the contents of a news portal: When browsed from the United States, it displays the latest headlines about the United States, but when browsed from France, the headlines concern the French news. So an l10n application not only provides content translation, but the content can be different from one localized version to another.

All in all, dealing with i18n and l10n means that the application can take care of the following:

• Text translation (interface, assets, and content)
• Standards and formats (dates, amounts, numbers, and so on)
• Localized content (many versions of a given object according to a country)

This chapter covers the way symfony deals with those elements and how you can use it to develop internationalized and localized applications.

User Culture

All the built-in i18n features in symfony are based on a parameter of the user session called the culture. The culture is the combination of the country and the language of the user, and it determines how the text and culture-dependent information are displayed. Since it is serialized in the user session, the culture is persistent between pages.

Setting the Default Culture

By default, the culture of new users is the default_culture. You can change this setting in the settings.yml configuration file, as shown in Listing 13-1.

Listing 13-1 - Setting the Default Culture, in frontend/config/settings.yml

all:
  .settings:
    default_culture: fr_FR

Keeping both the language and the country in the culture is necessary because you may have a different French translation for users from France, Belgium, or Canada, and a different Spanish content for users from Spain or Mexico. The language is coded in two lowercase characters, according to the ISO 639-1 standard (for instance, en for English). The country is coded in two uppercase characters, according to the ISO 3166-1 standard (for instance, GB for Great Britain).

Changing the Culture for a User

The user culture can be changed during the browsing session--for instance, when a user decides to switch from the English version to the French version of the application, or when a user logs in to the application and uses the language stored in his preferences. That's why the sfUser class offers getter and setter methods for the user culture. Listing 13-2 shows how to use these methods in an action.

Listing 13-2 - Setting and Retrieving the Culture in an Action

// Culture setter
$this->getUser()->setCulture('en_US');
 
// Culture getter
$culture = $this->getUser()->getCulture();
 => en_US

page:
  url: /:sf_culture/:page
  requirements: { sf_culture: (?:fr|en|de) }
  param: ...

article:
  url: /:sf_culture/:year/:month/:day/:slug
  requirements: { sf_culture: (?:fr|en|de) }
  param: ...

Determining the Culture Automatically

In many applications, the user culture is defined during the first request, based on the browser preferences. Users can define a list of accepted languages in their browser, and this data is sent to the server with each request, in the Accept-Language HTTP header. You can retrieve it in symfony through the sfWebRequest object. For instance, to get the list of preferred languages of a user in an action, type this:

$languages = $request->getLanguages();

The HTTP header is a string, but symfony automatically parses it and converts it into an array. So the preferred language of the user is accessible with $languages[0] in the preceding example.

It can be useful to automatically set the user culture to its preferred browser language in a site home page or in a filter for all pages. But as your website will probably only support a limited set of languages, it's better to use the getPreferredCulture() method. It returns the best language by comparing the user preferred languages and the supported languages:

$language = $request->getPreferredCulture(array('en', 'fr')); // the website is available in English and French

If there is no match, the method returns the first supported language (en in the preceding example).

Standards and Formats

The internals of a web application don't care about cultural particularities. Databases, for instance, use international standards to store dates, amounts, and so on. But when data is sent to or retrieved from users, a conversion needs to be made. Users won't understand timestamps, and they will prefer to declare their mother language as Français instead of French. So you will need assistance to do the conversion automatically, based on the user culture.

Outputting Data in the User's Culture

Once the culture is defined, the helpers depending on it will automatically have proper output. For instance, the format_number() helper automatically displays a number in a format familiar to the user, according to its culture, as shown in Listing 13-3.

Listing 13-3 - Displaying a Number for the User's Culture

<?php use_helper('Number') ?>
 
<?php $sf_user->setCulture('en_US') ?>
<?php echo format_number(12000.10) ?>
 => '12,000.10'
 
<?php $sf_user->setCulture('fr_FR') ?>
<?php echo format_number(12000.10) ?>
 => '12 000,10'

You don't need to explicitly pass the culture to the helpers. They will look for it themselves in the current session object. Listing 13-4 lists helpers that take into account the user culture for their output.

Listing 13-4 - Culture-Dependent Helpers

<?php use_helper('Date') ?>
 
<?php echo format_date(time()) ?>
 => '9/14/06'
 
<?php echo format_datetime(time()) ?>
 => 'September 14, 2006 6:11:07 PM CEST'
 
<?php use_helper('Number') ?>
 
<?php echo format_number(12000.10) ?>
 => '12,000.10'
 
<?php echo format_currency(1350, 'USD') ?>
 => '$1,350.00'
 
<?php use_helper('I18N') ?>
 
<?php echo format_country('US') ?>
 => 'United States'
 
<?php format_language('en') ?>
 => 'English'
 
<?php use_helper('Form') ?>
 
<?php echo input_date_tag('birth_date', mktime(0, 0, 0, 9, 14, 2006)) ?>
 => input type="text" name="birth_date" id="birth_date" value="9/14/06" size="11" />
 
<?php echo select_country_tag('country', 'US') ?>
 => <select name="country" id="country"><option value="AF">Afghanistan</option>
      ...
      <option value="GB">United Kingdom</option>
      <option value="US" selected="selected">United States</option>
      <option value="UM">United States Minor Outlying Islands</option>
      <option value="UY">Uruguay</option>
      ...
    </select>

The date helpers can accept an additional format parameter to force a culture-independent display, but you shouldn't use it if your application is internationalized.

Getting Data from a Localized Input

If it is necessary to show data in the user's culture, as for retrieving data, you should, as much as possible, push users of your application to input already internationalized data. This approach will save you from trying to figure out how to convert data with varying formats and uncertain locality. For instance, who might enter a monetary value with comma separators in an input box?

You can frame the user input format either by hiding the actual data (as in a select_country_tag()) or by separating the different components of complex data into several simple inputs.

For dates, however, this is often not possible. Users are used to entering dates in their cultural format, and you need to be able to convert such data to an internal (and international) format. This is where the sfI18N class applies. Listing 13-5 demonstrates how this class is used.

Listing 13-5 - Getting a Date from a Localized Format in an Action

$date= $request->getParameter('birth_date');
$user_culture = $this->getUser()->getCulture();
 
// Getting a timestamp
$timestamp = $this->getContext()->getI18N()->getTimestampForCulture($date, $user_culture);
 
// Getting a structured date
list($d, $m, $y) = $this->getContext()->getI18N()->getDateForCulture($date, $user_culture);

Text Information in the Database

A localized application offers different content according to the user's culture. For instance, an online shop can offer products worldwide at the same price, but with a custom description for every country. This means that the database must be able to store different versions of a given piece of data, and for that, you need to design your schema in a particular way and use culture each time you manipulate localized model objects.

Creating Localized Schema

For each table that contains some localized data, you should split the table in two parts: one table that does not have any i18n column, and the other one with only the i18n columns. The two tables are to be linked by a one-to-many relationship. This setup lets you add more languages when required without changing your model. Let's consider an example using a Product table.

First, create tables in the schema.yml file, as shown in Listing 13-6.

Listing 13-6 - Sample Schema for i18n Data, in config/schema.yml

my_connection:
  my_product:
    _attributes: { phpName: Product, isI18N: true, i18nTable: my_product_i18n }
    id:          { type: integer, required: true, primaryKey: true, autoincrement: true }
    price:       { type: float }

  my_product_i18n:
    _attributes: { phpName: ProductI18n }
    id:          { type: integer, required: true, primaryKey: true, foreignTable: my_product, foreignReference: id }
    culture:     { isCulture: true, type: varchar, size: 7, required: true, primaryKey: true }
    name:        { type: varchar, size: 50 }

Notice the isI18N and i18nTable attributes in the first table, and the special culture column in the second. All these are symfony-specific Propel enhancements.

The symfony automations can make this much faster to write. If the table containing internationalized data has the same name as the main table with _i18n as a suffix, and they are related with a column named id in both tables, you can omit the id and culture columns in the _i18n table as well as the specific i18n attributes for the main table; symfony will infer them. It means that symfony will see the schema in Listing 13-7 as the same as the one in Listing 13-6.

Listing 13-7 - Sample Schema for i18n Data, Short Version, in config/schema.yml

my_connection:
  my_product:
    _attributes: { phpName: Product }
    id:
    price:       float
  my_product_i18n:
    _attributes: { phpName: ProductI18n }
    name:        varchar(50)

Using the Generated I18n Objects

Once the corresponding object model is built (don't forget to call the propel:build-model task after each modification of the schema.yml), you can use your Product class with i18n support as if there were only one table, as shown in Listing 13-8.

Listing 13-8 - Dealing with i18n Objects

$product = ProductPeer::retrieveByPk(1);
$product->setName('Nom du produit'); // By default, the culture is the current user culture
$product->save();
 
echo $product->getName();
 => 'Nom du produit'
 
$product->setName('Product name', 'en'); // change the value for the 'en' culture
$product->save();
 
echo $product->getName('en');
 => 'Product name'

As for queries with the peer objects, you can restrict the results to objects having a translation for the current culture by using the doSelectWithI18n method, instead of the usual doSelect, as shown in Listing 13-10. In addition, it will create the related i18n objects at the same time as the regular ones, resulting in a reduced number of queries to get the full content (refer to Chapter 18 for more information about this method's positive impacts on performance).

Listing 13-10 - Retrieving Objects with an i18n Criteria

$c = new Criteria();
$c->add(ProductPeer::PRICE, 100, Criteria::LESS_THAN);
$products = ProductPeer::doSelectWithI18n($c, $culture);
// The $culture argument is optional
// The current user culture is used if no culture is given

So basically, you should never have to deal with the i18n objects directly, but instead pass the culture to the model (or let it guess it) each time you do a query with the regular objects.

Interface Translation

The user interface needs to be adapted for i18n applications. Templates must be able to display labels, messages, and navigation in several languages but with the same presentation. Symfony recommends that you build your templates with the default language, and that you provide a translation for the phrases used in your templates in a dictionary file. That way, you don't need to change your templates each time you modify, add, or remove a translation.

Configuring Translation

The templates are not translated by default, which means that you need to activate the template translation feature in the settings.yml file prior to everything else, as shown in Listing 13-11.

Listing 13-11 - Activating Interface Translation, in frontend/config/settings.yml

all:
  .settings:
    i18n: on

Using the Translation Helper

Let's say that you want to create a website in English and French, with English being the default language. Before even thinking about having the site translated, you probably wrote the templates something like the example shown in Listing 13-12.

Listing 13-12 - A Single-Language Template

Welcome to our website. Today's date is <?php echo format_date(date()) ?>

For symfony to translate the phrases of a template, they must be identified as text to be translated. This is the purpose of the __() helper (two underscores), a member of the I18N helper group. So all your templates need to enclose the phrases to translate in such function calls. Listing 13-12, for example, can be modified to look like Listing 13-13 (as you will see in the "Handling Complex Translation Needs" section later in this chapter, there is an even better way to call the translation helper in this example).

Listing 13-13 - A Multiple-Language-Ready Template

<?php use_helper('I18N') ?>
 
<?php echo __('Welcome to our website.') ?>
<?php echo __("Today's date is ") ?>
<?php echo format_date(date()) ?>

Using Dictionary Files

Each time the __() function is called, symfony looks for a translation of its argument in the dictionary of the current user's culture. If it finds a corresponding phrase, the translation is sent back and displayed in the response. So the user interface translation relies on a dictionary file.

The dictionary files are written in the XML Localization Interchange File Format (XLIFF), named according to the pattern messages.[language code].xml, and stored in the application i18n/ directory.

XLIFF is a standard format based on XML. As it is well known, you can use third-party translation tools to reference all text in your website and translate it. Translation firms know how to handle such files and to translate an entire site just by adding a new XLIFF translation.

Listing 13-14 shows an example of the XLIFF syntax with the messages.fr.xml file necessary to translate Listing 13-13 into French.

Listing 13-14 - An XLIFF Dictionary, in frontend/i18n/messages.fr.xml

<?xml version="1.0" ?>
<xliff version="1.0">
  <file original="global" source-language="en_US" datatype="plaintext">
    <body>
      <trans-unit id="1">
        <source>Welcome to our website.</source>
        <target>Bienvenue sur notre site web.</target>
      </trans-unit>
      <trans-unit id="2">
        <source>Today's date is </source>
        <target>La date d'aujourd'hui est </target>
      </trans-unit>
    </body>
  </file>
</xliff>

The source-language attribute must always contain the full ISO code of your default culture. Each translation is written in a trans-unit tag with a unique id attribute.

With the default user culture (set to en_US), the phrases are not translated and the raw arguments of the __() calls are displayed. The result of Listing 13-13 is then similar to Listing 13-12. However, if the culture is changed to fr_FR or fr_BE, the translations from the messages.fr.xml file are displayed instead, and the result looks like Listing 13-15.

Listing 13-15 - A Translated Template

Bienvenue sur notre site web. La date d'aujourd'hui est
<?php echo format_date(date()) ?>

If additional translations need to be done, simply add a new messages.``XX``.xml translation file in the same directory.

Managing Dictionaries

If your messages.XX.xml file becomes too long to be readable, you can always split the translations into several dictionary files, named by theme. For instance, you can split the messages.fr.xml file into these three files in the application i18n/ directory:

• navigation.fr.xml
• terms_of_service.fr.xml
• search.fr.xml

Note that as soon as a translation is not to be found in the default messages.XX.xml file, you must declare which dictionary is to be used each time you call the __() helper, using its third argument. For instance, to output a string that is translated in the navigation.fr.xml dictionary, write this:

<?php echo __('Welcome to our website', null, 'navigation') ?>

Another way to organize translation dictionaries is to split them by module. Instead of writing a single messages.XX.xml file for the whole application, you can write one in each modules/[module_name]/i18n/ directory. It makes modules more independent from the application, which is necessary if you want to reuse them, such as in plug-ins (see Chapter 17).

New in symfony 1.1

As updating the i18n dictionaries by hand is quite error prone, symfony provides a task to automate the process. The i18n:extract task parses a symfony application to extract all the strings that need to be translated. It takes an application and a culture as its arguments:

> php symfony i18n:extract frontend en

By default, the task does not modify your dictionaries, it just outputs the number of new and old i18n strings. To append the new strings to your dictionary, you can pass the --auto-save option:

> php symfony i18n:extract --auto-save frontend en

You can also delete old strings automatically by passing the --auto-delete option:

> php symfony i18n:extract --auto-save --auto-delete frontend en

Handling Other Elements Requiring Translation

The following are other elements that may require translation:

• Images, text documents, or any other type of assets can also vary according to the user culture. The best example is a piece of text with a special typography that is actually an image. For these, you can create subdirectories named after the user culture:

  <?php echo image_tag($sf_user->getCulture().'/myText.gif') ?>

• Error messages from validation files are automatically output by a __(), so you just need to add their translation to a dictionary to have them translated.

• The default symfony pages (page not found, internal server error, restricted access, and so on) are in English and must be rewritten in an i18n application. You should probably create your own default module in your application and use __() in its templates. Refer to Chapter 19 to see how to customize these pages.

Handling Complex Translation Needs

Translation only makes sense if the __() argument is a full sentence. However, as you sometimes have formatting or variables mixed with words, you could be tempted to cut sentences into several chunks, thus calling the helper on senseless phrases. Fortunately, the __() helper offers a replacement feature based on tokens, which will help you to have a meaningful dictionary that is easier to handle by translators. As with HTML formatting, you can leave it in the helper call as well. Listing 13-16 shows an example.

Listing 13-16 - Translating Sentences That Contain Code

// Base example
Welcome to all the <b>new</b> users.<br />
There are <?php echo count_logged() ?> persons logged.
 
// Bad way to enable text translation
<?php echo __('Welcome to all the') ?>
<b><?php echo __('new') ?></b>
<?php echo __('users') ?>.<br />
<?php echo __('There are') ?>
<?php echo count_logged() ?>
<?php echo __('persons logged') ?>
 
// Good way to enable text translation
<?php echo __('Welcome to all the <b>new</b> users') ?> <br />
<?php echo __('There are %1% persons logged', array('%1%' => count_logged())) ?>

In this example, the token is %1%, but it can be anything, since the replacement function used by the translation helper is strtr().

One of the common problems with translation is the use of the plural form. According to the number of results, the text changes but not in the same way according to the language. For instance, the last sentence in Listing 13-16 is not correct if count_logged() returns 0 or 1. You could do a test on the return value of this function and choose which sentence to use accordingly, but that would represent a lot of code. Additionally, different languages have different grammar rules, and the declension rules of plural can be quite complex. As this problem is very common, symfony provides a helper to deal with it, called format_number_choice(). Listing 13-17 demonstrates how to use this helper.

Listing 13-17 - Translating Sentences Depending on the Value of Parameters

<?php echo format_number_choice(
  '[0]Nobody is logged|[1]There is 1 person logged|(1,+Inf]There are %1% persons logged', array('%1%' => count_logged()), count_logged()) ?>

The first argument is the multiple possibilities of text. The second argument is the replacement pattern (as with the __() helper) and is optional. The third argument is the number on which the test is made to determine which text is taken.

The message/string choices are separated by the pipe (|) character followed by an array of acceptable values, using the following syntax:

• [1,2]: Accepts values between 1 and 2, inclusive
• (1,2): Accepts values between 1 and 2, excluding 1 and 2
• {1,2,3,4}: Only values defined in the set are accepted
• [-Inf,0): Accepts values greater or equal to negative infinity and strictly less than 0
• {n: n % 10 > 1 && n % 10 < 5} pliki: Matches numbers like 2, 3, 4, 22, 23, 24 (useful for languages like polish or russian) New in development version

Any nonempty combinations of the delimiters of square brackets and parentheses are acceptable.

The message will need to appear explicitly in the XLIFF file for the translation to work properly. Listing 13-18 shows an example.

Listing 13-18 - XLIFF Dictionary for a format_number_choice() Argument

...
<trans-unit id="3">
  <source>[0]Nobody is logged|[1]There is 1 person logged|(1,+Inf]There are %1% persons logged</source>
  <target>[0]Personne n'est connecté|[1]Une personne est connectée|(1,+Inf]Il y a %1% personnes en ligne</target>
</trans-unit>
...

all:
  .settings:
    charset: utf-8

Calling the Translation Helper Outside a Template

Not all the text that is displayed in a page comes from templates. That's why you often need to call the __() helper in other parts of your application: actions, filters, model classes, and so on. Listing 13-19 shows how to call the helper in an action by retrieving the current instance of the I18N object through the context singleton.

Listing 13-19 - Calling __() in an Action

$this->getContext()->getI18N()->__($text, $args, 'messages');

Summary

Handling internationalization and localization in web applications is painless if you know how to deal with the user culture. The helpers automatically take it into account to output correctly formatted data, and the localized content from the database is seen as if it were part of a simple table. As for the interface translation, the __() helper and XLIFF dictionary ensure that you will have maximum versatility with minimum work.