New in Symfony 2.6: Farewell to ICU component

"The big picture" of Symfony internationalization

To better understand the cause of this problem and its solution, it's important to understand The Big Picture of the projects and systems involved:

• The CLDR project collects and maintains internationalization data, such as country and language names, currency metadata, number formats, postal code and phone number formats. CLDR data is used in all smartphones, operating systems and important software applications developed by companies such as Apple, Google, Microsoft and IBM.
• The ICU project uses the CLDR data and builds C and Java classes on top of them, such as NumberFormatter, IntlDateFormatter, Collator and ResourceBundle.
• The PHP intl extension makes some ICU classes accessible in PHP, but it does not bundle the CLDR data. It uses the data installed globally on the system (which is independent of PHP).
• The Symfony Icu component includes all the CLDR data, because Symfony needs access to the data in all locales, independent of the system's configuration. We even offered different versions: if you didn't have the intl extension installed, you'd have Icu 1.0.x, which ships the data as .php files. With the intl extension, you'd have 1.1.x or 1.2.x which ships the data as binary files, readable using the ResourceBundle class.
• The Symfony Intl component does two things: first, it provides access to the data of the Icu component (Intl::get*Bundle()->get*()). Second, it provides a partial PHP implementation for some ICU classes (NumberFormatter) which you can use when intl extension is not installed.

Understanding the problem

As you may know, Composer uses two files called composer.json and composer.lock to manage your project's dependencies. The composer.lock file stores the hashes of the package versions you have installed.

The workflow that causes this problem is usually the following:

• Developer A, who has the intl extension, installs or updates Symfony.
• The composer.lock file will contain the Icu 1.2.x version.
• Developer A commits the composer.lock file to the repository.
• Developer B, who doesn't have the intl extension, installs the project with the usual composer install command.
• Composer tries to install Icu 1.2.x, which requires intl, and the result is the infamous symfony/icu v1.2.x requires lib-icu >=4.4 error.
• If Developer B executes composer update command, Composer will correctly detect that intl is not installed and it will use instead Icu 1.0.x.

Understanding the solution

In order to solve this problem, the Intl component now includes all the CLDR data. As a consequence, the Icu component has been deprecated because is no longer needed.

Moreover, when you didn't have the intl extension installed, previously you could only access to the CLDR data in English. Now, you can access to all data in all locales, independent of whether intl is installed or not.

Given the large amount of information contained in the CLDR data, you may be worried by the impact in the total Symfony download size. Even if the data is stored as JSON files instead of using a binary format, the total compressed size is just about 2 MB.

Note Most of the contents of this post have been written by Bernhard Schussek, who kindly explained me all the pieces involved in the Symfony internationalization sub-framework.