GNU gettext is an extension within PHP that must be included at the php.ini:

extension=php_gettext.dll #Windows
extension=gettext.so #Linux

The gettext functions implement an NLS (Native Language Support) API which can be used to internationalize your PHP applications.

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Translating strings can be done in PHP by setting the locale, setting up your translation tables and calling gettext() on any string you want to translate.

<?php
// Set language to French
putenv('LC_ALL=    fr_FR');
setlocale(LC_ALL, 'fr_FR');

// Specify location of translation tables for 'myPHPApp' domain
bindtextdomain("myPHPApp", "./locale");

// Select 'myPHPApp' domain
textdomain("myPHPApp");

myPHPApp.po

#: /Hello_world.php:56
msgid "Hello"
msgstr "Bonjour"

#: /Hello_world.php:242
msgid "How are you?"
msgstr "Comment allez-vous?"

gettext() loads a given post-complied .po file, a .mo. which maps your to-be translated strings as above.

After this small bit of setup code, translations will now be looked for in the following file:

• ./locale/fr_FR/LC_MESSAGES/myPHPApp.mo.

Whenever you call gettext('some string'), if 'some string' has been translated in the .mo file, the translation will be returned. Otherwise, 'some string' will be returned untranslated.

// Print the translated version of 'Welcome to My PHP Application'
echo gettext("Welcome to My PHP Application");

// Or use the alias _() for gettext()
echo _("Have a nice day");