Internationalization & Localization

One of the best ways for an application to reach a larger audience is to cater to multiple languages. This can often prove to be a daunting task, but the internationalization and localization features in CakePHP make it much easier.

First, it’s important to understand some terminology. Internationalization refers to the ability of an application to be localized. The term localization refers to the adaptation of an application to meet specific language (or culture) requirements (i.e. a “locale”). Internationalization and localization are often abbreviated as i18n and l10n respectively; 18 and 10 are the number of characters between the first and last character.

Setting Up Translations

There are only a few steps to go from a single-language application to a multi-lingual application, the first of which is to make use of the __() function in your code. Below is an example of some code for a single-language application:

<h2>Popular Articles</h2>

To internationalize your code, all you need to do is to wrap strings in __() like so:

<h2><?= __('Popular Articles') ?></h2>

Doing nothing else, these two code examples are functionally identical - they will both send the same content to the browser. The __() function will translate the passed string if a translation is available, or return it unmodified.

Language Files

Translations can be made available by using language files stored in the application. The default format for CakePHP translation files is the Gettext format. Files need to be placed under src/Locale/ and within this directory, there should be a subfolder for each language the application needs to support:


The default domain is ‘default’, therefore the locale folder should at least contain the default.po file as shown above. A domain refers to any arbitrary grouping of translation messages. When no group is used, then the default group is selected.

The core strings messages extracted from the CakePHP library can be stored separately in a file named cake.po in src/Locale/. The CakePHP localized library houses translations for the client-facing translated strings in the core (the cake domain). To use these files, link or copy them into their expected location: src/Locale/<locale>/cake.po. If your locale is incomplete or incorrect, please submit a PR in this repository to fix it.

Plugins can also contain translation files, the convention is to use the under_scored version of the plugin name as the domain for the translation messages:


Translation folders can be the two or three letter ISO code of the language or the full locale name such as fr_FR, es_AR, da_DK which contains both the language and the country where it is spoken.

An example translation file could look like this:

msgid "My name is {0}"
msgstr "Je m'appelle {0}"

msgid "I'm {0,number} years old"
msgstr "J'ai {0,number} ans"

Extract Pot Files with I18n Shell

To create the pot files from __() and other internationalized types of messages that can be found in the application code, you can use the i18n shell. Please read the following chapter to learn more.

Setting the Default Locale

The default locale can be set in your config/app.php file by setting App.defaultLocale:

'App' => [
    'defaultLocale' => env('APP_DEFAULT_LOCALE', 'en_US'),

This will control several aspects of the application, including the default translations language, the date format, number format and currency whenever any of those is displayed using the localization libraries that CakePHP provides.

Changing the Locale at Runtime

To change the language for translated strings you can call this method:

use Cake\I18n\I18n;

// Prior to 3.5 use I18n::locale()

This will also change how numbers and dates are formatted when using one of the localization tools.

Using Translation Functions

CakePHP provides several functions that will help you internationalize your application. The most frequently used one is __(). This function is used to retrieve a single translation message or return the same string if no translation was found:

echo __('Popular Articles');

If you need to group your messages, for example, translations inside a plugin, you can use the __d() function to fetch messages from another domain:

echo __d('my_plugin', 'Trending right now');


If you want to translate your plugins and they’re namespaced, you must name your domain string Namespace/PluginName. But the related language file will become plugins/Namespace/PluginName/src/Locale/plugin_name.po inside your plugin folder.

Sometimes translations strings can be ambiguous for people translating them. This can happen if two strings are identical but refer to different things. For example, ‘letter’ has multiple meanings in English. To solve that problem, you can use the __x() function:

echo __x('written communication', 'He read the first letter');

echo __x('alphabet learning', 'He read the first letter');

The first argument is the context of the message and the second is the message to be translated.

msgctxt "written communication"
msgid "He read the first letter"
msgstr "Er las den ersten Brief"

Using Variables in Translation Messages

Translation functions allow you to interpolate variables into the messages using special markers defined in the message itself or in the translated string:

echo __("Hello, my name is {0}, I'm {1} years old", ['Sara', 12]);

Markers are numeric, and correspond to the keys in the passed array. You can also pass variables as independent arguments to the function:

echo __("Small step for {0}, Big leap for {1}", 'Man', 'Humanity');

All translation functions support placeholder replacements:

__d('validation', 'The field {0} cannot be left empty', 'Name');

__x('alphabet', 'He read the letter {0}', 'Z');

The ' (single quote) character acts as an escape code in translation messages. Any variables between single quotes will not be replaced and is treated as literal text. For example:

__("This variable '{0}' be replaced.", 'will not');

By using two adjacent quotes your variables will be replaced properly:

__("This variable ''{0}'' be replaced.", 'will');

These functions take advantage of the ICU MessageFormatter so you can translate messages and localize dates, numbers and currency at the same time:

echo __(
    'Hi {0}, your balance on the {1,date} is {2,number,currency}',
    ['Charles', new FrozenTime('2014-01-13 11:12:00'), 1354.37]

// Returns
Hi Charles, your balance on the Jan 13, 2014, 11:12 AM is $ 1,354.37

Numbers in placeholders can be formatted as well with fine grain control of the output:

echo __(
    'You have traveled {0,number} kilometers in {1,number,integer} weeks',
    [5423.344, 5.1]

// Returns
You have traveled 5,423.34 kilometers in 5 weeks

echo __('There are {0,number,#,###} people on earth', 6.1 * pow(10, 8));

// Returns
There are 6,100,000,000 people on earth

This is the list of formatter specifiers you can put after the word number:

  • integer: Removes the decimal part
  • currency: Puts the locale currency symbol and rounds decimals
  • percent: Formats the number as a percentage

Dates can also be formatted by using the word date after the placeholder number. A list of extra options follows:

  • short
  • medium
  • long
  • full

The word time after the placeholder number is also accepted and it understands the same options as date.


Named placeholders are supported in PHP 5.5+ and are formatted as {name}. When using named placeholders pass the variables in an array using key/value pairs, for example ['name' => 'Sara', 'age' => 12].

It is recommended to use PHP 5.5 or higher when making use of internationalization features in CakePHP. The php5-intl extension must be installed and the ICU version should be above 48.x.y (to check the ICU version Intl::getIcuVersion()).


One crucial part of internationalizing your application is getting your messages pluralized correctly depending on the language they are shown. CakePHP provides a couple ways to correctly select plurals in your messages.

Using ICU Plural Selection

The first one is taking advantage of the ICU message format that comes by default in the translation functions. In the translations file you could have the following strings

msgid "{0,plural,=0{No records found} =1{Found 1 record} other{Found # records}}"
msgstr "{0,plural,=0{Ningún resultado} =1{1 resultado} other{# resultados}}"

msgid "{placeholder,plural,=0{No records found} =1{Found 1 record} other{Found {1} records}}"
msgstr "{placeholder,plural,=0{Ningún resultado} =1{1 resultado} other{{1} resultados}}"

And in the application use the following code to output either of the translations for such string:

__('{0,plural,=0{No records found }=1{Found 1 record} other{Found # records}}', [0]);

// Returns "Ningún resultado" as the argument {0} is 0


// Returns "1 resultado" because the argument {0} is 1

__('{placeholder,plural,=0{No records found} =1{Found 1 record} other{Found {1} records}}', [0, 'many', 'placeholder' => 2])

// Returns "many resultados" because the argument {placeholder} is 2 and
// argument {1} is 'many'

A closer look to the format we just used will make it evident how messages are built:

{ [count placeholder],plural, case1{message} case2{message} case3{...} ... }

The [count placeholder] can be the array key number of any of the variables you pass to the translation function. It will be used for selecting the correct plural form.

Note that to reference [count placeholder] within {message} you have to use #.

You can of course use simpler message ids if you don’t want to type the full plural selection sequence in your code

msgid "search.results"

Then use the new string in your code:

__('search.results', [2, 2]);

// Returns: "2 resultados"

The latter version has the downside that there is a need to have a translation messages file even for the default language, but has the advantage that it makes the code more readable and leaves the complicated plural selection strings in the translation files.

Sometimes using direct number matching in plurals is impractical. For example, languages like Arabic require a different plural when you refer to few things and other plural form for many things. In those cases you can use the ICU matching aliases. Instead of writing:

=0{No results} =1{...} other{...}

You can do:

zero{No Results} one{One result} few{...} many{...} other{...}

Make sure you read the Language Plural Rules Guide to get a complete overview of the aliases you can use for each language.

Using Gettext Plural Selection

The second plural selection format accepted is using the built-in capabilities of Gettext. In this case, plurals will be stored in the .po file by creating a separate message translation line per plural form:

# One message identifier for singular
msgid "One file removed"
# Another one for plural
msgid_plural "{0} files removed"
# Translation in singular
msgstr[0] "Un fichero eliminado"
# Translation in plural
msgstr[1] "{0} ficheros eliminados"

When using this other format, you are required to use another translation function:

// Returns: "10 ficheros eliminados"
$count = 10;
__n('One file removed', '{0} files removed', $count, $count);

// It is also possible to use it inside a domain
__dn('my_plugin', 'One file removed', '{0} files removed', $count, $count);

The number inside msgstr[] is the number assigned by Gettext for the plural form of the language. Some languages have more than two plural forms, for example Croatian:

msgid "One file removed"
msgid_plural "{0} files removed"
msgstr[0] "{0} datoteka je uklonjena"
msgstr[1] "{0} datoteke su uklonjene"
msgstr[2] "{0} datoteka je uklonjeno"

Please visit the Launchpad languages page for a detailed explanation of the plural form numbers for each language.

Creating Your Own Translators

If you need to diverge from CakePHP conventions regarding where and how translation messages are stored, you can create your own translation message loader. The easiest way to create your own translator is by defining a loader for a single domain and locale:

use Aura\Intl\Package;

I18n::setTranslator('animals', function () {
    $package = new Package(
        'default', // The formatting strategy (ICU)
        'default'  // The fallback domain
        'Dog' => 'Chien',
        'Cat' => 'Chat',
        'Bird' => 'Oiseau'

    return $package;
}, 'fr_FR');

The above code can be added to your config/bootstrap.php so that translations can be found before any translation function is used. The absolute minimum that is required for creating a translator is that the loader function should return a Aura\Intl\Package object. Once the code is in place you can use the translation functions as usual:

// Prior to 3.5 use I18n::locale()
__d('animals', 'Dog'); // Returns "Chien"

As you see, Package objects take translation messages as an array. You can pass the setMessages() method however you like: with inline code, including another file, calling another function, etc. CakePHP provides a few loader functions you can reuse if you just need to change where messages are loaded. For example, you can still use .po files, but loaded from another location:

use Cake\I18n\MessagesFileLoader as Loader;

// Load messages from src/Locale/folder/sub_folder/filename.po
// Prior to 3.5 use translator()
    new Loader('filename', 'folder/sub_folder', 'po'),

Creating Message Parsers

It is possible to continue using the same conventions CakePHP uses, but use a message parser other than PoFileParser. For example, if you wanted to load translation messages using YAML, you will first need to created the parser class:

namespace App\I18n\Parser;

class YamlFileParser

    public function parse($file)
        return yaml_parse_file($file);

The file should be created in the src/I18n/Parser directory of your application. Next, create the translations file under src/Locale/fr_FR/animals.yaml

Dog: Chien
Cat: Chat
Bird: Oiseau

And finally, configure the translation loader for the domain and locale:

use Cake\I18n\MessagesFileLoader as Loader;

// Prior to 3.5 use translator()
    new Loader('animals', 'fr_FR', 'yaml'),

Creating Generic Translators

Configuring translators by calling I18n::setTranslator() for each domain and locale you need to support can be tedious, specially if you need to support more than a few different locales. To avoid this problem, CakePHP lets you define generic translator loaders for each domain.

Imagine that you wanted to load all translations for the default domain and for any language from an external service:

use Aura\Intl\Package;

I18n::config('default', function ($domain, $locale) {
    $locale = Locale::parseLocale($locale);
    $language = $locale['language'];
    $messages = file_get_contents("$lang.json");

    return new Package(
        'default', // Formatter
        null, // Fallback (none for default domain)
        json_decode($messages, true)

The above example calls an example external service to load a JSON file with the translations and then just build a Package object for any locale that is requested in the application.

If you’d like to change how packages are loaded for all packages, that don’t have specific loaders set you can replace the fallback package loader by using the _fallback package:

I18n::config('_fallback', function ($domain, $locale) {
    // Custom code that yields a package here.

New in version 3.4.0: Replacing the _fallback loader was added in 3.4.0

Plurals and Context in Custom Translators

The arrays used for setMessages() can be crafted to instruct the translator to store messages under different domains or to trigger Gettext-style plural selection. The following is an example of storing translations for the same key in different contexts:

    'He reads the letter {0}' => [
        'alphabet' => 'Él lee la letra {0}',
        'written communication' => 'Él lee la carta {0}'

Similarly, you can express Gettext-style plurals using the messages array by having a nested array key per plural form:

    'I have read one book' => 'He leído un libro',
    'I have read {0} books' => [
        'He leído un libro',
        'He leído {0} libros'

Using Different Formatters

In previous examples we have seen that Packages are built using default as first argument, and it was indicated with a comment that it corresponded to the formatter to be used. Formatters are classes responsible for interpolating variables in translation messages and selecting the correct plural form.

If you’re dealing with a legacy application, or you don’t need the power offered by the ICU message formatting, CakePHP also provides the sprintf formatter:

return Package('sprintf', 'fallback_domain', $messages);

The messages to be translated will be passed to the sprintf() function for interpolating the variables:

__('Hello, my name is %s and I am %d years old', 'José', 29);

It is possible to set the default formatter for all translators created by CakePHP before they are used for the first time. This does not include manually created translators using the setTranslator() and config() methods:


Localizing Dates and Numbers

When outputting Dates and Numbers in your application, you will often need that they are formatted according to the preferred format for the country or region that you wish your page to be displayed.

In order to change how dates and numbers are displayed you just need to change the current locale setting and use the right classes:

use Cake\I18n\I18n;
use Cake\I18n\Time;
use Cake\I18n\Number;

// Prior to 3.5 use I18n::locale()

$date = new Time('2015-04-05 23:00:00');

echo $date; // Displays 05/04/2015 23:00

echo Number::format(524.23); // Displays 524,23

Make sure you read the Date & Time and Number sections to learn more about formatting options.

By default dates returned for the ORM results use the Cake\I18n\Time class, so displaying them directly in you application will be affected by changing the current locale.

Parsing Localized Datetime Data

When accepting localized data from the request, it is nice to accept datetime information in a user’s localized format. In a controller, or Dispatcher Filters you can configure the Date, Time, and DateTime types to parse localized formats:

use Cake\Database\Type;

// Enable default locale format parsing.

// Configure a custom datetime format parser format.

// You can also use IntlDateFormatter constants.
    ->setLocaleFormat([IntlDateFormatter::SHORT, -1]);

The default parsing format is the same as the default string format.

Automatically Choosing the Locale Based on Request Data

By using the LocaleSelectorFilter in your application, CakePHP will automatically set the locale based on the current user:

// in src/Application.php
use Cake\I18n\Middleware\LocaleSelectorMiddleware;

// Update the middleware function, adding the new middleware
public function middleware($middleware)
    // Add middleware and set the valid locales
    $middleware->add(new LocaleSelectorMiddleware(['en_US', 'fr_FR']));

// Prior to 3.3.0, use the DispatchFilter
// in config/bootstrap.php

// Restrict the locales to only en_US, fr_FR
DispatcherFactory::add('LocaleSelector', ['locales' => ['en_US', 'fr_FR']]);

The LocaleSelectorFilter will use the Accept-Language header to automatically set the user’s preferred locale. You can use the locale list option to restrict which locales will automatically be used.