BCP 47

PHP helpers to validate and normalize IETF BCP 47 language tag.

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Utility functions

$isValid = Toobo\Bcp47::isValidTag('i-klingon');  // true
$isValid = Toobo\Bcp47::isValidTag('xy');         // false

$filtered = Toobo\Bcp47::filterTag('EN-us');      // "en-US"
$filtered = Toobo\Bcp47::filterTag('fr-latn-fx'); // "fr-FR"

$isRTL = Toobo\Bcp47::isRtl('he');                // true
$isRTL = Toobo\Bcp47::isRtl('en-us');             // false

var_export(Toobo\Bcp47::splitTag('En-ca-Newfound'));
array (
  'language' => 'en',
  'extLang' => '',
  'script' => '',
  'region' => 'CA',
  'variant' => 'newfound',
  'extension' => '',
  'privateUse' => '',
)

The Bcp47Tag class

The Toobo\Bcp47Tag class offers an API similar to the utility functions, but it ensures it encapsulates a valid tag, because it throws when instantiated with an invalid tag.

The class is Stringable and JsonSerializable, and it also implements the Bcp47Code interface defined by the wikimedia/bcp-47-code package.

$tag = Toobo\Bcp47Tag::new('En-ca-Newfound');

assert($tag->isSameCodeAs(Toobo\Bcp47Tag::new('en-CA-newfound')) === true);

assert($tag->language() === 'en');
assert($tag->extLang() === null);
assert($tag->script() === null);
assert($tag->region() === 'CA');
assert($tag->variant() === 'newfound');
assert($tag->extension() === null);
assert($tag->privateUse() === null);
assert($tag->isRtl() === false);

assert((string) $tag === 'en-CA-newfound');
assert($tag->toBcp47Code() === 'en-CA-newfound');
assert(json_encode($tag) === '{"language":"en","region":"CA","variant":"newfound"}');

Validation

The Bcp47Tag class, as well as the Bcp47::isValidTag(), Bcp47::filterTag(), and Bcp47::splitTag() functions, all do validation.

The class throw on instantiation for invalid tags, while the functions returns, respectively, false, null, and an array with all empty items.

The validation is not just about the format but also the actual values. For example, xy-IT looks like a valid tag, but the language "xy" does not exist, so the the tag is not valid.

The validation apply to all subtags (but "extension" and "privateUse"), and also across subtags. For example, the tag ca-valencia is valid (Valencia variant of the Catalan language), but en-valencia is not, despite the language "en" and the variant "valencia" being valid per-se, because there is no "valencia" variant for the English language.

Validation is done by comparing the values with the up-to-date list of all the registered BCP 47 subtags, which includes over 8000 languages, and several hundreds of scripts, regions, and variants.

Normalization

The Bcp47Tag class, as well as both Bcp47::filterTag() and Bcp47::splitTag() functions "normalize" the given tag.

Normalization includes:

• Replace deprecated values with the new accepted value, when available. For example, the region code for the "Democratic Republic of the Congo" (formerly "Zaire") "ZR" is replaced with "CD".
• Case normalization (all lowercase, but uppercase region and title-case script.
• Replacement of numeric region codes with 2-chars alpha code, when available.
• Replacement of 3-chars language code (ISO 639-3) with 2-chars code (ISO 636-1), when available.

FAQ

• Why is Bc47 an enum?

This package's utility functions are stateless and pure PHP functions.

However, plain PHP functions can't be autoloaded. By using a case-less PHP enum, we get autoloading, but unlike when using a class, we prevent anyone to extend or instantiate the class without intervening on the runtime code.

A case-less PHP enum is a de facto autoload-enabling namespace for functions.

Installation

Best served via Composer, the package name is toobo/bcp47.

composer require "toobo/bcp47:^1"

Requirements

BCP 47 requires PHP 8.3+, and requires via Composer:

• "wikimedia/bcp-47-code" (GPL v2)

When installed for development, it also requires via Composer:

• "phpunit/phpunit" (BSD-3-Clause)
• "inpsyde/php-coding-standards" (MIT)
• "vimeo/psalm" (MIT)

Security Issues

If you have identified a security issue, please email giuseppe.mazzapica [at] gmail.com and do not file an issue as they are public.

License

Copyright (c), Giuseppe Mazzapica, and contributors.

This software is released under the "MIT" license.