This method may be called by the template to change the current output language.

Its arguments are a list of possible languages (use func_get_args() to get the argument array). The first known language should be used by your service.

<?php
require_once 'PHPTAL/TranslationService.php';

class MyTranslator implements PHPTAL_TranslationService {
...
    public function setLanguage(){
        $langs = func_get_args();
        foreach ($langs as $lang){
            // if $lang known use it and stop the loop
            $this->_currentLang = $lang;
            return;
        }
    }
    ...
    private $_currentLang;
}
?>

If you decided to store your translations into separate files, one for each application, for example, this method allows you to select the translation domain from your templates (i18n:domain).

<?php
require_once 'PHPTAL/TranslationService.php';

class MyTranslator implements PHPTAL_TranslationService {
    ...
    public function useDomain($domain){
        if (!array_key_exists($domain, $this->_domains)){
            $file = "domains/$this->_currentLang/$domain.php";
            $this->_domains[$domain] = include($file);
        }
        $this->_currentDomain = $this->_domains[$domain];
    }
    ...
    private $_currentDomain;
    private $_domains = array();
}
?>

The above example is a possible translation solution where keys are stored in php files which return an associative array of key => translation.

This method matches i18n:name calls. It builds an interpolation context for later translate calls.

<?php
require_once 'PHPTAL/TranslationService.php';

class MyTranslator implements PHPTAL_TranslationService {
    ...
    public function setVar($key, $value){
        $this->_context[$key] = $value;
    }
    ...
    private $_context = array();
}
?>

The last and most important method to implement, it asks your service to translate the specified key for the currently selected language.

<?php
require_once 'PHPTAL/TranslationService.php';

class MyTranslator implements PHPTAL_TranslationService {
    ...
    public function translate($key){
        $value = $this->_currentDomain[$key];
        
        // interpolate ${myvar} using context associative array
        while (preg_match('/\${(.*?)\}/sm', $value, $m)){
            list($src,$var) = $m;
            if (!array_key_exists($var, $this->_context)){
                $err = sprintf('Interpolation error, var "%s" not set', 
                               $var);
                throw new Exception($err);
            }
            $value = str_replace($src, $this->_context[$var], $value);
        }
        
        return $value;
    }
    ...
}
?>