Internationalizing PHP Applications With TMX

Background on Zend_Translate

If you’re not familiar with Zend_Translate, here’s a quick overview; Zend_Translate allows you to quickly and effectively implement Internationalisation (I18N) in your web applications. Zend_Translate provides the following key features:

• Multiple source formats (or adapters)
• Thread-safe gettext support
• An easy and generic api
• Detection of the users language
• Automatic source detection

But for remainder of this article, I’m going to focus on the multiple source adapters.

Translation Adapters

If you’re not familiar with them, adapters are what store the website content in your chosen base language and in a translated version for one, or several, desired languages, that you believe your website visitors are keen to view your site in. These adapters come in a variety of forms, from the simplest ones, being a CSV file and a PHP array, to the more complex and esoteric ones, being TBX and TMX.

Using a PHP Array

$english = array(
    'message1' => 'message1',
    'message2' => 'message2',
    'message3' => 'message3'
);

$german = array(
    'message1' => 'Nachricht1',
    'message2' => 'Nachricht2',
    'message3' => 'Nachricht3'
);

$translate = new Zend_Translate(
    array(
        'adapter' => 'array',
        'content' => $english,
        'locale'  => 'en'
    )
);

$translate->addTranslation(
  array('content' => $german, 'locale' => 'de')
);

Using a CSV File

Example CSV File

message1;Nachricht1
message2;Nachricht2

$translate = new Zend_Translate(
    array(
        'adapter' => 'csv',
        'content' => '/path/to/mytranslation.csv',
        'locale'  => 'de'
    )
);

$translate->addTranslation(
    array(
        'content' => 'path/to/other.csv',
        'locale' => 'fr'
    )
);

You can see that in both examples, the initial content, in English, was created and used to initialise the Zend_Translate object and that, after that, the additional translations were added to the adapter with the addTranslation method.

Given this, it becomes, relatively painless to add as many sets of translation information as you need in a consistent and predictable manner.

Displaying View Content

Once you’ve made your choice of adapter and you’ve created and loaded the required source files, actually using it in a Zend Framework project, to display internationalised content, becomes very simple.

I’ll assume that you’re following the standard Zend Framework approach and your view scripts are responsible for outputting your user interface text, whether that’s a menu, footer, copyright notice or something else, and it’s not managed in code.

Given that, you would, normally, do something like the following:

print $this->escape('copyrightNotice');.

Right? Well, once the translation adapter is setup, only a small change is required to implement internationalisation. Your view script above now becomes the following:

print $this->translate(escape('copyrightNotice'));

Now I don’t want to get in to any kind of security debate here, we’re just focussing on the key elements of translation and internationalisation – right?

How do you determine the language choice

Now that you’ve got your source files and view configured to translate your content, all that remains is for the user to choose their language. This is done through a variety of methods, but the one that I find simplest is through their letting the users browser’s language option set it automatically.

Depending on what they’ve got it set to, your website will display content in that language if it’s available, or fall back to your default language. You don’t have to do anything fancy, just let the browser specify the choice and away you go. To do this, when you configure the Zend_Translate resource, say in your bootstrap file, you’d set the option to AUTO as in the following code.

If you want to know more about Zend_Translate, there is an excellent series of video casts over at ZendCasts.com.

Quick Plug: Jon’s* video casts are always timely and accurate, presented in a clear and unambiguously manner each week. Tell him Matt from Malt Blue said hi.*

So What is TMX

TMX (or Translation Memory eXchange) is one of the more advanced source adapters for Zend_Translate. Based on XML, TMX is an international standard for storing and delivering translation information. According to Wikipedia, TMX:

TMX (Translation Memory eXchange) is the vendor-neutral open XML standard for the exchange of Translation Memory (TM) data created by Computer Aided Translation (CAT) and localization tools. The purpose of TMX is to allow* easier exchange of translation memory data between tools and/or translation vendors with little or no loss of critical data during the process*.

It is a bit unwieldy at first, but if you’re familiar with XML, you’ll get a grasp on it quite quickly. Have a look at the sample below and I’ll take you through the key points.

<?xml version="1.0" ?>
<!DOCTYPE tmx SYSTEM "tmx14.dtd">
<tmx version="1.4">
   <header creationtoolversion="1.0.0" datatype="winres" segtype="sentence"
           adminlang="en-us" srclang="de-at" o-tmf="abc"
           creationtool="XYZTool" >
   </header>
   <body>
       <tu tuid='message1'>
           <tuv xml:lang="de"><seg>Nachricht1</seg></tuv>
           <tuv xml:lang="en"><seg>message1</seg></tuv>
       </tu>
       <tu tuid='message2'>
           <tuv xml:lang="de"><seg>Nachricht2</seg></tuv>
           <tuv xml:lang="en"><seg>message2</seg></tuv>
       </tu>
   </body>
</tmx>

$translate = new Zend_Translate(
    array(
        'adapter' => 'tmx',
        'content' => 'path/to/mytranslation.tmx',
        'locale'  => 'en'
    )
);

What’s it all mean

Well, there is a bit to it and you can find a host of links in the links section. For the purposes of this post, I’m sticking to some of the more regularly used elements.

There are two sections to the document: header and body and the file is always written out in Unicode format. The header is metadata about the file and the body is where the translation information is stored.

The Header

In the header section, delimited by