Standards

A collection of standards as PHP Enums

Daily updated from their sources, whether it is ISO or IANA directly, or a maintaining party like the SIX Group or the US Library of Congress.

Setup

Note Make sure you are running PHP 8.1 or higher to use this package

To start right away, run the following command in your composer project;

composer require prinsfrank/standards

Or for development only;

composer require prinsfrank/standards --dev

Daily updated from their source

How this package works

This package implements a bunch of specs as PHP Enums, so you can typehint them in methods. Currently, all specs are implemented as backed enums. That means that besides a name, they have also an internal 'value', either as an integer or a string.

In the Country, Currency and language specifications, there is also a relation between different enums. For example, the Alpha2 country code 'NL' is related to the Alpha3 'NLD', the numeric value '528' and the name 'Netherlands (the)'. Internally, these specs rely on the fact that the keys for these values are identical, so it is possible to convert between these.

Entities and their relations

All specifications in this package are closely related, except for the Http status code and methods. Not all relations are bidirectional though. For example, a language tag is build up of a language and optionally a country, but only a country cannot be converted to a language tag.

Below you can find an overview of all the relationships between specifications.

erDiagram
    Country {
        class CountryAlpha2
        class CountryAlpha3
        class CountryNumeric
        class CountryName
    }
    GeographicRegion {
        class GeographicRegion
    }
    CountryGroup {
        class BRICS
        class EEA
        class EFTA
        class EU
        class NATO
        class Schengen
    }
    CountryCallingCode {
        class CountryCallingCode
    }
    CountrySubdivision {
        class CountrySubdivision
    }
    Currency {
        class CurrencyAlpha3
        class CurrencyName
        class CurrencyNumeric
    }
    CurrencySymbol {
        class CurrencySymbol
    }
    NationalCallPrefix {
        class NationalCallPrefix
    }
    InternationalCallPrefix {
        class InternationalCallPrefix
    }
    Language {
        class LanguageName
        class LanguageAlpha2
        class LanguageAlpha3Common
        class LanguageAlpha3Bibliographic
        class LanguageAlpha3Terminology
        class LanguageAlpha3Extensive
    }
    Script {
        class ScriptAlias
        class ScriptCode
        class ScriptName
        class ScriptNumber
    }
    LanguageTag {
        class LanguageTag
        class LanguageTagVariant
        class PrivateUsePrimarySubtag
        class SingleCharacterSubtag
    }
    HttpMethod {
        class HtppMethod
    }
    HttpStatusCode {
        class HttpStatusCode
    }
    TLD {
        class CountryCodeTLD
        class GenericRestrictedTLD
        class GenericTLD
        class InfrastructureTLD
        class SponsoredTLD
        class TestTLD
    }

    Country ||--o{ CountrySubdivision: ""
    Country ||--o{ Country: ""
    GeographicRegion }|--o{ Country: ""
    GeographicRegion ||--o{ GeographicRegion: ""
    Language }o--o{ Country: ""
    Country }|--o{ CountryGroup: ""
    Country }|--o{ CountryCallingCode: ""
    Country }o--o{ Currency: ""
    Country }|--o{ NationalCallPrefix: ""
    Country }|--o{ InternationalCallPrefix: ""
    Currency }|--o| CurrencySymbol: ""
    LanguageTag ||--o{ LanguageTag: ""
    Language }|--o{ LanguageTag: ""
    Script |o--o{ LanguageTag: ""
    Country |o--o{ LanguageTag: ""
    TLD ||--o| Country: ""
    LanguageTag }o--o| GeographicRegion: ""

Upgrading

This package adheres to semver. This means that there are no breaking changes between minor releases (for example from 1.1 to 1.2), but that breaking changes are released as a major release (for example from 1.x to 2.x). To read about upgrading from one major release to the next, please refer to the UPGRADING.md file in the root of this project.

Some powerful use cases

Format a complete phone number string based on the users country;

Automatically select a supported language from an HTTP request;

Listing all country calling codes sorted by country name in a dropdown;

Country (ISO3166-1)

:mortar_board: Alpha2/3 country codes are always UPPERCASE to avoid confusion with language codes. It is recommended to use Alpha2/Alpha3 codes when exposing the specification in APIs

At a glance

All the Alpha2, Alpha3, Numeric and Name values have a corresponding enum in the other country enums. These can be converted using their corresponding methods (toAlpha2, toAlpha3 etc...).

Country group membership can be checked by calling the isMemberOf method, supplying the FQN of a class that implements the GroupInterface. Several country groups are available: BRICS, EEA, EFTA etc. Countries can also have subdivisions, which can be of several types: countries, provinces, etc.

CountryAlpha2::from('NL');                                      // CountryAlpha2::Netherlands
CountryNumeric::from('528');                                    // CountryNumeric::Netherlands
CountryNumeric::fromInt(528);                                   // CountryNumeric::Netherlands
CountryAlpha3::from('NLD');                                     // CountryAlpha3::Netherlands
CountryAlpha3::from('NLD')->value;                              // 'NLD'
CountryAlpha3::from('NLD')->name;                               // 'Netherlands'
CountryAlpha3::from('NLD')->toCountryAlpha2()->value;           // 'NL'
CountryAlpha3::from('NLD')->toCountryNumeric()->value;          // '528'
CountryAlpha3::from('NLD')->toCountryNumeric()->valueAsInt();   // 528
CountryAlpha3::from('NLD')->isMemberOf(EU::class);              // true
CountryAlpha2::Netherlands;                                     // CountryAlpha2::Netherlands

CountryAlpha2::Vanuatu->getSubdivisions();                      // [CountrySubdivision::Vanuatu_province_Malampa, CountrySubdivision::Vanuatu_province_Penama, CountrySubdivision::Vanuatu_province_Sanma, CountrySubdivision::Vanuatu_province_Shefa, CountrySubdivision::Vanuatu_province_Tafea, CountrySubdivision::Vanuatu_province_Torba]

CountryAlpha2::Aruba->getParentCountry();                       // CountryAlpha2::Netherlands
CountryAlpha2::Netherlands->getSubCountries();                  // [CountryAlpha2::Aruba, CountryAlpha2::Curacao, CountryAlpha2::Sint_Maarten_Dutch_part, CountryAlpha2::Bonaire_Sint_Eustatius_and_Saba]

CountryAlpha3::from('NLD')->getCountryCallingCodes();           // [CountryCallingCode::Netherlands_Kingdom_of_the]
CountryAlpha3::from('NLD')->getCountryCallingCodes()[0]->value; // 31

CountryAlpha3::from('NLD')->getInternationalCallPrefix();        // InternationalCallPrefix::_00
CountryAlpha3::from('NLD')->getInternationalCallPrefix()->value; // '00'

CountryAlpha3::from('NLD')->getNationalCallPrefix();             // NationalCallPrefix::_0
CountryAlpha3::from('NLD')->getNationalCallPrefix()->value;      // '0'

CountryAlpha3::from('NLD')->getFlagEmoji();                      // '🇳🇱' (This might not be displayed correctly in this readme if you're on windows, see 'https://prinsfrank.nl/2021/01/25/Non-existing-flag-emojis-on-windows to make these flag emojis visible for Windows users.')
CountryAlpha3::from('NLD')->getCurrenciesAlpha3();               // [CurrencyAlpha3::Euro]
CountryAlpha3::from('NLD')->getOfficialAndDeFactoLanguages();    // [LanguageAlpha2::Dutch_Flemish]

CountryAlpha3::from('NLD')->getNameInLanguage(LanguageAlpha2::Dutch_Flemish): // 'Nederland'
CountryAlpha3::from('NLD')->getNameInLanguage(LanguageAlpha2::English):       // 'Netherlands'

CountryAlpha3::from('NLD')->formatNumber(42.42, LanguageAlpha2::Dutch_Flemish); // '42,42'

public function foo(CountryAlpha2 $countryAlpha2) {}             // Use spec as typehint to enforce valid value

Country Calling Codes (ITU-T E.164)

:mortar_board: Country calling codes can be anywhere from 1 to 3 digits, and can span several countries. There are no leading zeros in this specification.

At a glance

Country calling codes are quite straight forward. One country can have multiple country calling codes though, And one country calling code can span multiple countries. That's why the forCountry and getCountriesAlpha2 both return an array of country calling codes/countries and not a single item.

CountryCallingCode::from(1);                    // CountryCallingCode::Integrated_numbering_plan
CountryCallingCode::from(31);                   // CountryCallingCode::Netherlands_Kingdom_of_the
CountryCallingCode::from(31)->value;            // 31
CountryCallingCode::from(31)->name;             // 'Netherlands_Kingdom_of_the'
CountryCallingCode::Netherlands_Kingdom_of_the; // CountryCallingCode::Netherlands_Kingdom_of_the

CountryCallingCode::from(31)->getCountriesAlpha2(); // [CountryAlpha2::Netherlands]
CountryCallingCode::from(7)->getCountriesAlpha2();  // [CountryAlpha2::Kazakhstan, CountryAlpha2::Russian_Federation]

CountryCallingCode::forCountry(CountryAlpha2::Netherlands); // [CountryCallingCode::Netherlands_Kingdom_of_the]

public function foo(CountryCallingCode $countryCallingCode) {} // Use spec as typehint to enforce valid value

Currency (ISO4217)

:mortar_board: Alpha3 codes are uppercase. When communicating or storing currencies, it is recommended to do so using the Alpha3 or Numeric representation.

At a glance

All the Alpha3, Numeric and Name values have a corresponding enum in the other currency enums. These can be converted using their corresponding methods (toCurrencyAlpha3, etc...). A fourth enum is available that maps all currencies to a currency symbol, that can be accessed by calling the 'getSymbol' method.

CurrencyAlpha3::from('EUR');                               // CurrencyAlpha3::Euro
CurrencyAlpha3::from('EUR')->value;                        // 'EUR'
CurrencyAlpha3::from('EUR')->lowercaseValue();             // 'eur'
CurrencyAlpha3::from('EUR')->toCurrencyName()->value;      // 'Euro'
CurrencyAlpha3::from('EUR')->getSymbol();                  // CurrencySymbol::Euro
CurrencyAlpha3::from('EUR')->getSymbol()->value;           // '€'
CurrencyAlpha3::from('EUR')->toCurrencyNumeric()->value;   // '978'
CurrencyAlpha3::from('EUR')->getMinorUnits();              // 2
CurrencyNumeric::from('978');                              // CurrencyNumeric::Euro
CurrencyNumeric::fromInt(978);                             // CurrencyNumeric::Euro
CurrencyNumeric::from('978')->value;                       // '978'
CurrencyNumeric::from('978')->valueAsInt();                // 978
CurrencySymbol::from('€');                                 // CurrencySymbol::Euro
CurrencySymbol::from('€')->value;                          // '€'
CurrencySymbol::forCurrency(CurrencyAlpha3::Euro);         // CurrencySymbol::Euro
CurrencySymbol::forCurrency(CurrencyNumeric::Euro);        // CurrencySymbol::Euro
CurrencySymbol::forCurrency(CurrencyName::Euro);           // CurrencySymbol::Euro
CurrencySymbol::forCurrency(CurrencyNumeric::from('978')); // CurrencySymbol::Euro
CurrencyAlpha3::Euro;                                      // CurrencyAlpha3::Euro

CurrencyAlpha3::Euro->format(42.42, CountryAlpha2::Netherlands);                                // '€ 42,42'
CurrencyAlpha3::Euro->format(42.42, CountryAlpha2::Netherlands, LanguageAlpha2::Dutch_Flemish); // '€ 42,42'

CurrencyAlpha3::Norwegian_Krone->getCountriesAlpha2();     // [CountryAlpha2::Bouvet_Island, CountryAlpha2::Norway, CountryAlpha2::Svalbard_Jan_Mayen]

public function foo(CurrencyAlpha3 $currencyAlpha3) {}     // Use spec as typehint to enforce valid value

HTTP Methods

At a glance

HttpMethod::from('POST');        // HttpMethod::Post
HttpMethod::from('POST')->value; // 'POST'
HttpMethod::from('POST')->name;  // Post
HttpMethod::Post;                // HttpMethod::Post

public function foo(HttpMethod $httpMethod) {} // Use spec as typehint to enforce valid value

HTTP Status Codes

At a glance

HttpStatusCode::from(404);       // HttpStatusCode::Not_Found
HttpStatusCode::from(404->value; // 404
HttpStatusCode::from(404->name;  // Not_Found
HttpStatusCode::Not_Found;       // HttpStatusCode::Not_Found

public function foo(HttpStatusCode $httpStatusCode) {} // Use spec as typehint to enforce valid value

International Call Prefixes (ITU-T E.164)

Different countries have different international call prefixes. This is a spec extracted from ITU-T E.164 listing all possible international call prefixes.

At a glance

InternationalCallPrefix::from('0');                // InternationalCallPrefix::_0
InternationalCallPrefix::from('0')->value;         // '0'
InternationalCallPrefix::from('0')->name;          // '_0'
InternationalCallPrefix::_0;                       // InternationalCallPrefix::_0
InternationalCallPrefix::_0->getCountriesAlpha2(); // [CountryAlpha2::Samoa]

InternationalCallPrefix::forCountry(CountryAlpha2::Netherlands);  // InternationalCallPrefix::_00
InternationalCallPrefix::forCountry(CountryAlpha3::Netherlands);  // InternationalCallPrefix::_00
InternationalCallPrefix::forCountry(CountryNumeric::Netherlands); // InternationalCallPrefix::_00
InternationalCallPrefix::forCountry(CountryName::Netherlands);    // InternationalCallPrefix::_00

public function foo(InternationalCallPrefix $internationalCallPrefix) {} // Use spec as typehint to enforce valid value

Language (ISO639)

:mortar_board: Language codes are always in lowercase to avoid confusion with country codes.

:mortar_board: The alpha2 specification has 184 languages, the alpha3 Bibliographic/Terminology specification has 486 languages and the alpha3 Extensive specification has 7908 languages.

:mortar_board: If you have to choose between the alpha3 Bibliographic and Terminology specification, the Terminology specification is more widely used.

At a glance

There are four language code specifications:

• 184 Language Alpha2 (ISO 639-1)
• 486 Language Alpha3 Bibliographic (ISO 639-2)
• 486 Language Alpha3 Terminology (ISO 639-2)
• 7908 Language Alpha3 Extensive (ISO 639-3)

As you see, the Bibliographic and Terminology specifications have an identical number of languages, so there is a one-to-one relation between these.

LanguageAlpha2::from('nl');                                         // LanguageAlpha2::Dutch_Flemish
LanguageAlpha2::from('nl')->value;                                  // 'nl'
LanguageAlpha2::from('nl')->name;                                   // 'Dutch_Flemish'
LanguageAlpha2::from('nl')->toLanguageAlpha3Bibliographic();        // LanguageAlpha3Bibliographic::Dutch_Flemish
LanguageAlpha2::from('nl')->toLanguageAlpha3Bibliographic()->value; // 'dut'
LanguageAlpha2::from('nl')->toLanguageAlpha3Terminology();          // LanguageAlpha3Terminology::Dutch_Flemish
LanguageAlpha2::from('nl')->toLanguageAlpha3Terminology()->value;   // 'nld'
LanguageAlpha2::from('nl')->toLanguageName()->value;                // 'Dutch; Flemish'

LanguageAlpha3Terminology::from('nld');                             // LanguageAlpha3Terminology::Dutch_Flemish
LanguageAlpha3Bibliographic::from('dut');                           // LanguageAlpha3Bibliographic::Dutch_Flemish

LanguageAlpha3Extensive::from('nld');                               // LanguageAlpha3Extensive::Dutch
LanguageAlpha3Extensive::from('dse');                               // LanguageAlpha3Extensive::Dutch_Sign_Language

LanguageAlpha2::Dutch_Flemish->getNameInLanguage(LanguageAlpha2::Dutch_Flemish); // 'Nederlands'
LanguageAlpha2::Dutch_Flemish->getNameInLanguage(LanguageAlpha2::English);       // 'Dutch'

public function foo(LanguageAlpha2 $languageAlpha2);                // Use spec as typehint to enforce valid value

Language Tags (RFC 5646)

:mortar-board: Language tags always have a primary tag, and can have an extension, script, region, one or more variants, one or more extension and/or a private subtag.

At a glance

LanguageTag::tryFromString('');            // null
LanguageTag::fromString();                 // InvalidArgumentException
LanguageTag::fromString('nl');             // LanguageTag(LanguageAlpha2::Dutch_Flemish);
LanguageTag::fromString('i-enochian');     // LanguageTag(SingleCharacterSubtag::GRANDFATHERED, privateUseSubtag: 'enochian')
LanguageTag::fromString('zh-Hant');        // LanguageTag(LanguageAlpha2::Chinese, script: ScriptSubtag::Han_Traditional_variant)
LanguageTag::fromString('sr-Cyrl');        // LanguageTag(LanguageAlpha2::Serbian, scriptSubtag: ScriptCode::Cyrillic)
LanguageTag::fromString('zh-cmn-Hans-CN'); // LanguageTag(LanguageAlpha2::Chinese, LanguageAlpha3Extensive::Mandarin_Chinese, ScriptCode::Han_Simplified_variant, CountryAlpha2::China)
LanguageTag::fromString('sl-rozaj-biske'); // LanguageTag(LanguageAlpha2::Slovenian, variantSubtag: [LanguageTagVariant::Rezijan, LanguageTagVariant::The_Bila_dialect_of_Resian])
LanguageTag::fromString('de-CH-1901');     // LanguageTag(LanguageAlpha2::German, regionSubtag: CountryAlpha2::Switzerland, variantSubtag: [LanguageTagVariant::Traditional_German_orthography])

LanguageTag::fromString('de-CH-1901')->primaryLanguageSubtag; // LanguageAlpha2::German
LanguageTag::fromString('de-CH-1901')->regionSubtag;          // CountryAlpha2::Switzerland

LanguageAlpha2::Dutch_Flemish->toLanguageTag(); // 'nl'
LanguageAlpha2::German->toLanguageTag(regionSubtag: CountryAlpha2::Switzerland, variantSubtag: [LanguageTagVariant::Traditional_German_orthography]); // 'de-CH-1901'

public function foo(LanguageTag $languageTag): {} // Use spec as typehint to enforce valid value

Geographic regions (M49)

:mortar_board: Geographic regions are represented by three digits. Leading zeros are required. Each geographic region can span multiple other geographic regions or countries.

At a glance

GeographicRegion::from('150');        // GeographicRegion::Europe
GeographicRegion::from('150')->value; // '150'
GeographicRegion::from('150')->name;  // Europe
GeographicRegion::Europe;             // GeographicRegion::Europe

GeographicRegion::from('150')->getDirectSubRegions();   // [GeographicRegion::Eastern_Europe, GeographicRegion::Northern_Europe, ...]
GeographicRegion::from('150')->getAllSubRegions();      // [GeographicRegion::Eastern_Europe, GeographicRegion::Northern_Europe, ...]

GeographicRegion::from('150')->getDirectSubCountries(); // []
GeographicRegion::from('150')->getAllSubCountries();    // [CountryNumeric::Belarus, CountryNumeric::Bulgaria, ...]

public function foo(GeographicRegion $geographicRegion) {} // Use spec as typehint to enforce valid value

National Call Prefixes (ITU-T E.164)

Different countries have different national call prefixes;

At a glance

NationalCallPrefix::from('0');                // NationalCallPrefix::_0
NationalCallPrefix::from('0')->value;         // '0'
NationalCallPrefix::from('0')->name;          // '_0'
NationalCallPrefix::_0;                       // NationalCallPrefix::_0

NationalCallPrefix::forCountry(CountryAlpha2::Netherlands);  // NationalCallPrefix::_0
NationalCallPrefix::forCountry(CountryAlpha3::Netherlands);  // NationalCallPrefix::_0
NationalCallPrefix::forCountry(CountryNumeric::Netherlands); // NationalCallPrefix::_0
NationalCallPrefix::forCountry(CountryName::Netherlands);    // NationalCallPrefix::_0

public function foo(NationalCallPrefix $nationalCallPrefix) {} // Use spec as typehint to enforce valid value

Scripts

At a glance

ScriptAlias::from('Latin');                    // ScriptAlias::Latin
ScriptAlias::from('Latin')->value;             // 'Latin'
ScriptAlias::from('Latin')->name;              // 'Latin'
ScriptAlias::Latin;                            // ScriptAlias::Latin
ScriptAlias::from('Latin')->toScriptCode();    // ScriptCode::Latin
ScriptCode::from('Latn');                      // ScriptCode::Latin
ScriptName::from('Latin');                     // ScriptName::Latin
ScriptNumber::from('215');                     // ScriptNumber::Latin

ScriptAlias::Latin->isSupportedByPHPRegex();   // true
ScriptAlias::allForString('еюeuеюευ');         // [ScriptAlias::Cyrillic, ScriptAlias::Greek, ScriptAlias::Latin]
ScriptAlias::hasMultipleForString('еюeuеюευ'); // true
ScriptAlias::mostCommonInString('еюeuеюευ');   // ScriptAlias::Cyrillic

public function foo(ScriptAlias $scriptAlias) {} // Use spec as typehint to enforce valid value

TLDs

There are currently 6 types of Top Level Domains:

• CountryCode
• GenericRestricted
• Generic
• Infrastructure
• Sponsored
• Test

Most of these specification have several TLDs that are 'unmanaged' and are thus not currently available. Those are marked as deprecated, but are kept in the specification. There is one exception: All Test TLDs are always unmanaged and are thus never marked as deprecated.

CountryCodeTLD

Where a TLD is marked as unmanaged by IANA it is marked as deprecated.

CountryCodeTLD::from('nl');                      // CountryCodeTLD::nl
CountryCodeTLD::nl;                              // CountryCodeTLD::nl
CountryCodeTLD::from('nl')->value;               // 'nl'
CountryCodeTLD::from('nl')->name;                // 'nl'
CountryCodeTLD::from('nl')->isAssigned();        // true
CountryCodeTLD::from('nl')->getCountryAlpha2();  // CountryAlpha2::Netherlands
CountryCodeTLD::from('nl')->getCountryAlpha3();  // CountryAlpha3::Netherlands
CountryCodeTLD::from('nl')->getCountryNumeric(); // CountryNumeric::Netherlands

public function foo(CountryCodeTLD $countryCodeTLD) {} // Use spec as typehint to enforce valid value

GenericRestrictedTLD

Where a TLD is marked as unmanaged by IANA it is marked as deprecated.

GenericRestrictedTLD::from('name');                // GenericRestrictedTLD::name
GenericRestrictedTLD::name;                        // GenericRestrictedTLD::name
GenericRestrictedTLD::from('name')->value;         // 'name'
GenericRestrictedTLD::from('name')->name;          // 'name'
GenericRestrictedTLD::from('name')->isAssigned();  // true

public function foo(GenericRestrictedTLD $genericRestrictedTLD) {} // Use spec as typehint to enforce valid value

GenericTLD

Where a TLD is marked as unmanaged by IANA it is marked as deprecated.

GenericTLD::from('aaa');                // GenericTLD::aaa
GenericTLD::aaa;                        // GenericTLD::aaa
GenericTLD::from('aaa')->value;         // 'aaa'
GenericTLD::from('aaa')->name;          // 'aaa'
GenericTLD::from('aaa')->isAssigned();  // true

public function foo(GenericTLD $genericTLD) {} // Use spec as typehint to enforce valid value

InfrastructureTLD

Where a TLD is marked as unmanaged by IANA it is marked as deprecated.

InfrastructureTLD::from('arpa');                // InfrastructureTLD::arpa
InfrastructureTLD::arpa;                        // InfrastructureTLD::arpa
InfrastructureTLD::from('arpa')->value;         // 'arpa'
InfrastructureTLD::from('arpa')->name;          // 'arpa'
InfrastructureTLD::from('arpa')->isAssigned();  // true

public function foo(InfrastructureTLD $infrastructureTLD) {} // Use spec as typehint to enforce valid value

SponsoredTLD

Where a TLD is marked as unmanaged by IANA it is marked as deprecated.

SponsoredTLD::from('aero');                // SponsoredTLD::aero
SponsoredTLD::arpa;                        // SponsoredTLD::aero
SponsoredTLD::from('aero')->value;         // 'aero'
SponsoredTLD::from('aero')->name;          // 'aero'
SponsoredTLD::from('aero')->isAssigned();  // true

public function foo(SponsoredTLD $sponsoredTLD) {} // Use spec as typehint to enforce valid value

TestTLD

All Test TLDs are always unmanaged and are thus never marked as deprecated.

TestTLD::from('テスト');              // TestTLD::tesuto_katakana
TestTLD::tesuto_katakana;            // TestTLD::tesuto_katakana
TestTLD::from('テスト')->value;       // 'テスト'
TestTLD::from('テスト')->name;        // 'tesuto_katakana'
TestTLD::from('テスト')->isAssigned() // false

public function foo(TestTLD $testTLD) {} // Use spec as typehint to enforce valid value