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Internationalization Using PHP and GetText
Posted on Monday, September 17 @ 05:21:59 EDT
Topic: Localization

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If you are a web developer using PHP from small web applications to large corporate portals with millions of page views, you may suddenly find that you need your site or application translated to another language. When your company opens www.company.com.br you need your application in Portuguese, then you'll need it in Japanese and so on. You don't have a "translation" problem, you have an internationalization problem.

Translating only implies simple string translation of code, you may do it in a clever way or a painful (very) way scanning all the code and translating strings. This method tends to produce errors (Have you ever seen a site in Spanglish?) and it is not reusable, just a patch. Internationalization defines a strategy to build sites and applications that you can easily translate into other languages. This is the goal of this article.



Enter GNU

GNU has a very good set of tools to produce internationalizable applications called gettext, it was developed with "C" and "C++" applications in mind but is also very easy to use in other languages such as PHP. Gettext is probably installed on your Unix station, try a gettext command like 'gettext' from the command line to see if you have it. If not (rare) download the package from ftp.gnu.org and install it. If you have gettext the next stage is to use it from PHP.

Internationalizing PHP Scripts

To use gettext in your PHP scripts you'll have to modify all your scripts, however this will have to be done only once. The modifications are not very difficult and you'll probably want to build some utility to scan the code and prompt 'want to modify this?' etc... If you don't want to do that, no problem at all. So what do you have to do in your code? Very simple just replace all the "strings" with something like:

print(_("Hello world"));

Yes, you use the very unknown PHP function "underscore", which is an alias to the not-short-to-write "gettext" function. Every string that you may translate sometime will have to be translated. Once you get used to this and see the advantages you'll find that you always write your strings wrapped with the "_" function.

Extracting Strings from the Code

Gettext provides a utility called 'xgettext' to extract all the strings from your scripts to a file called a "po" file, you have to use:

$xgettext -a src/*.php

To extract all the strings. Read the GNU's documentation for 'xgettext' for more options . After xgettexting your code you will have a 'messages.po' file which may look like this one:

# SOME DESCRIPTIVE TITLE.
# Copyright (C) YEAR Free Software Foundation, Inc.
# FIRST AUTHOR , YEAR.
#
#, fuzzy
msgid ""
msgstr ""
"Project-Id-Version: PACKAGE VERSION "
"POT-Creation-Date: 2000-12-08 19:15-0300 "
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE "
"Last-Translator: FULL NAME "
"Language-Team: LANGUAGE "
"MIME-Version: 1.0 "
"Content-Type: text/plain; charset=CHARSET "
"Content-Transfer-Encoding: ENCODING "

#: prueba.php:12
msgid "Hello world"
msgstr ""

#: prueba.php:12 prueba.php:13
msgid ""
msgstr ""

#: prueba.php:13
msgid "This is a test"
msgstr ""

This will be the file that you have to pass to translators, they will have to set msgstr for each entry to the proper translation of the string for the target language. You can add comments (using #comment) for each entry to provide context if needed such as:

#: prueba.php:12
# This is displayed at the beginning of the script
msgid "Hello world"
msgstr ""

Etc, after this you have a "master" po file where all the msgstr strings are "". Using gettext on a string that is not translated will simply output the msgid. This is a good feature.

Once translators have translated the 'messages.po' file, you'll have several files for different languages. It is time yo use them from PHP.

Producing mo Files

You have to produce a .mo file to use gettext, this is done using the 'msgfmt' command for each .po file:

$msgfmt messages.po -o messages.mo

Setting up Directories

The best way to use gettext is to build a "locale" directory in some branch of your code tree and inside this directory you create one subdirectory for each language, inside each language's direcory you create an LC_MESSAGES directory, where you put .mo and .po files for the language. Example:

/src
/locale/en/LC_MESSAGES/messages.mo
messages.po
es/LC_MESSAGES/messages.po
messages.mo

Use this URL http://lcweb.loc.gov/standards/iso639-2/bibcodes.html#op to find the 2 character codes for languages. It's nice to follow standards...

You'd probably start liking your "neat" structure of languages a lot, you are ready to decide which language to use in PHP, simply add, in your main script, this code:

// Set language to Spanish
putenv ("LC_ALL=es");

// Specify location of translation tables
bindtextdomain ("messages", "./locale");

// Choose domain
textdomain ("messages");

The important line is putenv("LC_ALL=es") which basically tells which language to use, with this PHP will use your /locale/es/LC_MESSAGES/messages.mo file to translate all the strings. If you want a different language just change:

putenv ("LC_ALL=en);

And "auto-magically" you have an English application.

Conclusions and Code

Gettext is a very good way to standardize your PHP code to support internationalization, you modify or write your code only once and you can have your site or application in several different languages with only a minor modification. One side effect of this strategy is that you have to make sure that all the strings are set in the content or logic layer not in the presentation layer. If you use XSLT to parse XML generated from PHP for example you'll have to make sure that no strings are added in the XSLT layer. I think this is quite good.

In inter.tar.gz you'll find a subtree that you can put wherever you want inside your document tree, I ship examples in English and Spanish, change the environment variable from "en" to "es" and browse "prueba.php" (the Spanish file),and see the changes. Edit the .po files and rebuild the .mo files using msgfmt to play the translator role. As perl fans says "there are many ways of doing things..." this is a neat one, try it.



Author: Luis Argerich (salutia.com)
Publishing date: 14.12.2000 17:53






 
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