# Internationalization Functions

# 简介

Internationalization extension (further is referred as Intl) is a wrapper for » ICU library, enabling PHP programmers to perform various locale-aware operations including but not limited to formatting, transliteration, encoding conversion, calendar operations, » UCA-conformant collation, locating text boundaries and working with locale identifiers, timezones and graphemes.

It tends to closely follow ICU APIs, so that people having experience working with ICU in either C/C++ or Java could easily use the PHP API. Also, this way ICU documentation would be useful to understand various ICU functions.

Intl consists of several modules, each of them exposes the corresponding ICU API:

- Collator: provides string comparison capability with support for appropriate locale-sensitive sort orderings.
- Number Formatter: allows to display number according to the localized format or given pattern or set of rules, and to parse strings into numbers.
- Message Formatter: allows to create messages incorporating data (such as numbers or dates) formatted according to given pattern and locale rules, and parse messages extracting data from them. It can handle plurals, locale-aware numbers, currencies, conditions and much more.
- Normalizer: provides a function to transform text into one of the Unicode normalization forms, and provides a routine to test if a given string is already normalized.
- Locale: provides interaction with locale identifiers in the form of functions to get subtags from locale identifier; parse, compose, match(lookup and filter) locale identifiers.
- Calendar: provides a class which could be used for locale-aware calendar operations and getting various information such as timezone for locale chosen, first day of week or if it's daylight saving time now.
- Timezone: provides a wrapper around the » "Olson" database which has information about all the timezones around the world.
- Date formatter: allows to display date and time according to the localized format or given pattern or set of rules, and to parse strings into date and time.
- Transliterator: allows getting latin representation of strings in various languages.

## Links

- » Miscellaneous ICU docs

- » ICU User Guide

- » Unicode Collation Algorithm

- 安装/配置
  - 需求
  - 安装
  - 运行时配置
- 预定义常量
- 示例
  - Basic usage of this extension
- Collator — The Collator class
  - Collator::asort — Sort array maintaining index association
  - Collator::compare — Compare two Unicode strings
  - Collator::__construct — Create a collator
  - Collator::create — Create a collator
  - Collator::getAttribute — Get collation attribute value
  - Collator::getErrorCode — Get collator's last error code
  - Collator::getErrorMessage — Get text for collator's last error code
  - Collator::getLocale — Get the locale name of the collator
  - Collator::getSortKey — Get sorting key for a string
  - Collator::getStrength — Get current collation strength
  - Collator::setAttribute — Set collation attribute
  - Collator::setStrength — Set collation strength
  - Collator::sort — Sort array using specified collator
  - Collator::sortWithSortKeys — Sort array using specified collator and sort keys
- NumberFormatter — The NumberFormatter class
  - NumberFormatter::create — Create a number formatter
  - NumberFormatter::format — Format a number
  - NumberFormatter::formatCurrency — Format a currency value
  - NumberFormatter::getAttribute — Get an attribute
  - NumberFormatter::getErrorCode — Get formatter's last error code
  - NumberFormatter::getErrorMessage — Get formatter's last error message
  - NumberFormatter::getLocale — Get formatter locale
  - NumberFormatter::getPattern — Get formatter pattern
  - NumberFormatter::getSymbol — Get a symbol value
  - NumberFormatter::getTextAttribute — Get a text attribute
  - NumberFormatter::parse — Parse a number
  - NumberFormatter::parseCurrency — Parse a currency number
  - NumberFormatter::setAttribute — Set an attribute
  - NumberFormatter::setPattern — Set formatter pattern
  - NumberFormatter::setSymbol — Set a symbol value
  - NumberFormatter::setTextAttribute — Set a text attribute
- Locale — The Locale class
  - Locale::acceptFromHttp — Tries to find out best available locale based on HTTP "Accept-Language" header
  - Locale::canonicalize — Canonicalize the locale string
  - Locale::composeLocale — Returns a correctly ordered and delimited locale ID
  - Locale::filterMatches — Checks if a language tag filter matches with locale
  - Locale::getAllVariants — Gets the variants for the input locale
  - Locale::getDefault — Gets the default locale value from the INTL global 'default_locale'
  - Locale::getDisplayLanguage — Returns an appropriately localized display name for language of the inputlocale
  - Locale::getDisplayName — Returns an appropriately localized display name for the input locale
  - Locale::getDisplayRegion — Returns an appropriately localized display name for region of the input locale
  - Locale::getDisplayScript — Returns an appropriately localized display name for script of the input locale
  - Locale::getDisplayVariant — Returns an appropriately localized display name for variants of the input locale
  - Locale::getKeywords — Gets the keywords for the input locale
  - Locale::getPrimaryLanguage — Gets the primary language for the input locale
  - Locale::getRegion — Gets the region for the input locale
  - Locale::getScript — Gets the script for the input locale
  - Locale::isRightToLeft — Check whether a locale uses a right-to-left writing system
  - Locale::lookup — Searches the language tag list for the best match to the language
  - Locale::parseLocale — Returns a key-value array of locale ID subtag elements
  - Locale::setDefault — Sets the default runtime locale
- Normalizer — The Normalizer class
  - Normalizer::getRawDecomposition — Gets the Decomposition_Mapping property for the given UTF-8 encoded code point
  - Normalizer::isNormalized — Checks if the provided string is already in the specified normalization form
  - Normalizer::normalize — Normalizes the input provided and returns the normalized string
- MessageFormatter — The MessageFormatter class
  - MessageFormatter::create — Constructs a new Message Formatter
  - MessageFormatter::format — Format the message
  - MessageFormatter::formatMessage — Quick format message
  - MessageFormatter::getErrorCode — Get the error code from last operation
  - MessageFormatter::getErrorMessage — Get the error text from the last operation
  - MessageFormatter::getLocale — Get the locale for which the formatter was created
  - MessageFormatter::getPattern — Get the pattern used by the formatter
  - MessageFormatter::parse — Parse input string according to pattern
  - MessageFormatter::parseMessage — Quick parse input string
  - MessageFormatter::setPattern — Set the pattern used by the formatter
- IntlCalendar — The IntlCalendar class
  - IntlCalendar::add — Add a (signed) amount of time to a field
  - IntlCalendar::after — Whether this objectʼs time is after that of the passed object
  - IntlCalendar::before — Whether this objectʼs time is before that of the passed object
  - IntlCalendar::clear — Clear a field or all fields
  - IntlCalendar::__construct — Private constructor for disallowing instantiation
  - IntlCalendar::createInstance — Create a new IntlCalendar
  - IntlCalendar::equals — Compare time of two IntlCalendar objects for equality
  - IntlCalendar::fieldDifference — Calculate difference between given time and this objectʼs time
  - IntlCalendar::fromDateTime — Create an IntlCalendar from a DateTime object or string
  - IntlCalendar::get — Get the value for a field
  - IntlCalendar::getActualMaximum — The maximum value for a field, considering the objectʼs current time
  - IntlCalendar::getActualMinimum — The minimum value for a field, considering the objectʼs current time
  - IntlCalendar::getAvailableLocales — Get array of locales for which there is data
  - IntlCalendar::getDayOfWeekType — Tell whether a day is a weekday, weekend or a day that has a transition between the two
  - IntlCalendar::getErrorCode — Get last error code on the object
  - IntlCalendar::getErrorMessage — Get last error message on the object
  - IntlCalendar::getFirstDayOfWeek — Get the first day of the week for the calendarʼs locale
  - IntlCalendar::getGreatestMinimum — Get the largest local minimum value for a field
  - IntlCalendar::getKeywordValuesForLocale — Get set of locale keyword values
  - IntlCalendar::getLeastMaximum — Get the smallest local maximum for a field
  - IntlCalendar::getLocale — Get the locale associated with the object
  - IntlCalendar::getMaximum — Get the global maximum value for a field
  - IntlCalendar::getMinimalDaysInFirstWeek — Get minimal number of days the first week in a year or month can have
  - IntlCalendar::getMinimum — Get the global minimum value for a field
  - IntlCalendar::getNow — Get number representing the current time
  - IntlCalendar::getRepeatedWallTimeOption — Get behavior for handling repeating wall time
  - IntlCalendar::getSkippedWallTimeOption — Get behavior for handling skipped wall time
  - IntlCalendar::getTime — Get time currently represented by the object
  - IntlCalendar::getTimeZone — Get the objectʼs timezone
  - IntlCalendar::getType — Get the calendar type
  - IntlCalendar::getWeekendTransition — Get time of the day at which weekend begins or ends
  - IntlCalendar::inDaylightTime — Whether the objectʼs time is in Daylight Savings Time
  - IntlCalendar::isEquivalentTo — Whether another calendar is equal but for a different time
  - IntlCalendar::isLenient — Whether date/time interpretation is in lenient mode
  - IntlCalendar::isSet — Whether a field is set
  - IntlCalendar::isWeekend — Whether a certain date/time is in the weekend
  - IntlCalendar::roll — Add value to field without carrying into more significant fields
  - IntlCalendar::set — Set a time field or several common fields at once
  - IntlCalendar::setDate — Set a date fields
  - IntlCalendar::setDateTime — Set a date and time fields
  - IntlCalendar::setFirstDayOfWeek — Set the day on which the week is deemed to start
  - IntlCalendar::setLenient — Set whether date/time interpretation is to be lenient
  - IntlCalendar::setMinimalDaysInFirstWeek — Set minimal number of days the first week in a year or month can have
  - IntlCalendar::setRepeatedWallTimeOption — Set behavior for handling repeating wall times at negative timezone offset transitions
  - IntlCalendar::setSkippedWallTimeOption — Set behavior for handling skipped wall times at positive timezone offset transitions
  - IntlCalendar::setTime — Set the calendar time in milliseconds since the epoch
  - IntlCalendar::setTimeZone — Set the timezone used by this calendar
  - IntlCalendar::toDateTime — Convert an IntlCalendar into a DateTime object
- IntlGregorianCalendar — The IntlGregorianCalendar class
  - IntlGregorianCalendar::__construct — Create the Gregorian Calendar class
  - IntlGregorianCalendar::createFromDate — Create a new IntlGregorianCalendar instance from date
  - IntlGregorianCalendar::createFromDateTime — Create a new IntlGregorianCalendar instance from date and time
  - IntlGregorianCalendar::getGregorianChange — Get the Gregorian Calendar change date
  - IntlGregorianCalendar::isLeapYear — Determine if the given year is a leap year
  - IntlGregorianCalendar::setGregorianChange — Set the Gregorian Calendar the change date
- IntlTimeZone — The IntlTimeZone class
  - IntlTimeZone::__construct — Private constructor to disallow direct instantiation
  - IntlTimeZone::countEquivalentIDs — Get the number of IDs in the equivalency group that includes the given ID
  - IntlTimeZone::createDefault — Create a new copy of the default timezone for this host
  - IntlTimeZone::createEnumeration — Get an enumeration over time zone IDs associated with the given country or offset
  - IntlTimeZone::createTimeZone — Create a timezone object for the given ID
  - IntlTimeZone::createTimeZoneIDEnumeration — Get an enumeration over system time zone IDs with the given filter conditions
  - IntlTimeZone::fromDateTimeZone — Create a timezone object from DateTimeZone
  - IntlTimeZone::getCanonicalID — Get the canonical system timezone ID or the normalized custom time zone ID for the given time zone ID
  - IntlTimeZone::getDisplayName — Get a name of this time zone suitable for presentation to the user
  - IntlTimeZone::getDSTSavings — Get the amount of time to be added to local standard time to get local wall clock time
  - IntlTimeZone::getEquivalentID — Get an ID in the equivalency group that includes the given ID
  - IntlTimeZone::getErrorCode — Get last error code on the object
  - IntlTimeZone::getErrorMessage — Get last error message on the object
  - IntlTimeZone::getGMT — Create GMT (UTC) timezone
  - IntlTimeZone::getIanaID — Translate a timezone identifier to its IANA equivalent
  - IntlTimeZone::getID — Get timezone ID
  - IntlTimeZone::getIDForWindowsID — Translate a Windows timezone into a system timezone
  - IntlTimeZone::getOffset — Get the time zone raw and GMT offset for the given moment in time
  - IntlTimeZone::getRawOffset — Get the raw GMT offset (before taking daylight savings time into account
  - IntlTimeZone::getRegion — Get the region code associated with the given system time zone ID
  - IntlTimeZone::getTZDataVersion — Get the timezone data version currently used by ICU
  - IntlTimeZone::getUnknown — Get the "unknown" time zone
  - IntlTimeZone::getWindowsID — Translate a system timezone into a Windows timezone
  - IntlTimeZone::hasSameRules — Check if this zone has the same rules and offset as another zone
  - IntlTimeZone::toDateTimeZone — Convert to DateTimeZone object
  - IntlTimeZone::useDaylightTime — Check if this time zone uses daylight savings time
- IntlDateFormatter — The IntlDateFormatter class
  - IntlDateFormatter::create — Create a date formatter
  - IntlDateFormatter::format — Format the date/time value as a string
  - IntlDateFormatter::formatObject — Formats an object
  - IntlDateFormatter::getCalendar — Get the calendar type used for the IntlDateFormatter
  - IntlDateFormatter::getDateType — Get the datetype used for the IntlDateFormatter
  - IntlDateFormatter::getErrorCode — Get the error code from last operation
  - IntlDateFormatter::getErrorMessage — Get the error text from the last operation
  - IntlDateFormatter::getLocale — Get the locale used by formatter
  - IntlDateFormatter::getPattern — Get the pattern used for the IntlDateFormatter
  - IntlDateFormatter::getTimeType — Get the timetype used for the IntlDateFormatter
  - IntlDateFormatter::getTimeZoneId — Get the timezone-id used for the IntlDateFormatter
  - IntlDateFormatter::getCalendarObject — Get copy of formatterʼs calendar object
  - IntlDateFormatter::getTimeZone — Get formatterʼs timezone
  - IntlDateFormatter::isLenient — Get the lenient used for the IntlDateFormatter
  - IntlDateFormatter::localtime — Parse string to a field-based time value
  - IntlDateFormatter::parse — Parse string to a timestamp value
  - IntlDateFormatter::parseToCalendar — Parse a string into a timestamp, updating an open calendar
  - IntlDateFormatter::setCalendar — Sets the calendar type used by the formatter
  - IntlDateFormatter::setLenient — Set the leniency of the parser
  - IntlDateFormatter::setPattern — Set the pattern used for the IntlDateFormatter
  - IntlDateFormatter::setTimeZone — Sets formatterʼs timezone
- ResourceBundle — The ResourceBundle class
  - ResourceBundle::count — Get number of elements in the bundle
  - ResourceBundle::create — Create a resource bundle
  - ResourceBundle::get — Get data from the bundle
  - ResourceBundle::getErrorCode — Get bundle's last error code
  - ResourceBundle::getErrorMessage — Get bundle's last error message
  - ResourceBundle::getLocales — Get supported locales
- Spoofchecker — The Spoofchecker class
  - Spoofchecker::areConfusable — Checks if given strings can be confused
  - Spoofchecker::__construct — Constructor
  - Spoofchecker::isSuspicious — Checks if a given text contains any suspicious characters
  - Spoofchecker::setAllowedChars — Set the set of characters allowed when running checks
  - Spoofchecker::setAllowedLocales — Locales to use when running checks
  - Spoofchecker::setChecks — Set the checks to run
  - Spoofchecker::setRestrictionLevel — Set the restriction level
- Transliterator — The Transliterator class
  - Transliterator::__construct — Private constructor to deny instantiation
  - Transliterator::create — Create a transliterator
  - Transliterator::createFromRules — Create transliterator from rules
  - Transliterator::createInverse — Create an inverse transliterator
  - Transliterator::getErrorCode — Get last error code
  - Transliterator::getErrorMessage — Get last error message
  - Transliterator::listIDs — Get transliterator IDs
  - Transliterator::transliterate — Transliterate a string
- IntlBreakIterator — The IntlBreakIterator class
  - IntlBreakIterator::__construct — Private constructor for disallowing instantiation
  - IntlBreakIterator::createCharacterInstance — Create break iterator for boundaries of combining character sequences
  - IntlBreakIterator::createCodePointInstance — Create break iterator for boundaries of code points
  - IntlBreakIterator::createLineInstance — Create break iterator for logically possible line breaks
  - IntlBreakIterator::createSentenceInstance — Create break iterator for sentence breaks
  - IntlBreakIterator::createTitleInstance — Create break iterator for title-casing breaks
  - IntlBreakIterator::createWordInstance — Create break iterator for word breaks
  - IntlBreakIterator::current — Get index of current position
  - IntlBreakIterator::first — Set position to the first character in the text
  - IntlBreakIterator::following — Advance the iterator to the first boundary following specified offset
  - IntlBreakIterator::getErrorCode — Get last error code on the object
  - IntlBreakIterator::getErrorMessage — Get last error message on the object
  - IntlBreakIterator::getLocale — Get the locale associated with the object
  - IntlBreakIterator::getPartsIterator — Create iterator for navigating fragments between boundaries
  - IntlBreakIterator::getText — Get the text being scanned
  - IntlBreakIterator::isBoundary — Tell whether an offset is a boundaryʼs offset
  - IntlBreakIterator::last — Set the iterator position to index beyond the last character
  - IntlBreakIterator::next — Advance the iterator the next boundary
  - IntlBreakIterator::preceding — Set the iterator position to the first boundary before an offset
  - IntlBreakIterator::previous — Set the iterator position to the boundary immediately before the current
  - IntlBreakIterator::setText — Set the text being scanned
- IntlRuleBasedBreakIterator — The IntlRuleBasedBreakIterator class
  - IntlRuleBasedBreakIterator::__construct — Create iterator from ruleset
  - IntlRuleBasedBreakIterator::getBinaryRules — Get the binary form of compiled rules
  - IntlRuleBasedBreakIterator::getRules — Get the rule set used to create this object
  - IntlRuleBasedBreakIterator::getRuleStatus — Get the largest status value from the break rules that determined the current break position
  - IntlRuleBasedBreakIterator::getRuleStatusVec — Get the status values from the break rules that determined the current break position
- IntlCodePointBreakIterator — The IntlCodePointBreakIterator class
  - IntlCodePointBreakIterator::getLastCodePoint — Get last code point passed over after advancing or receding the iterator
- IntlDatePatternGenerator — The IntlDatePatternGenerator class
  - IntlDatePatternGenerator::create — Creates a new IntlDatePatternGenerator instance
  - IntlDatePatternGenerator::getBestPattern — Determines the most suitable date/time format
- IntlPartsIterator — The IntlPartsIterator class
  - IntlPartsIterator::getBreakIterator — Get IntlBreakIterator backing this parts iterator
- UConverter — The UConverter class
  - UConverter::__construct — Create UConverter object
  - UConverter::convert — Convert string from one charset to another
  - UConverter::fromUCallback — Default "from" callback function
  - UConverter::getAliases — Get the aliases of the given name
  - UConverter::getAvailable — Get the available canonical converter names
  - UConverter::getDestinationEncoding — Get the destination encoding
  - UConverter::getDestinationType — Get the destination converter type
  - UConverter::getErrorCode — Get last error code on the object
  - UConverter::getErrorMessage — Get last error message on the object
  - UConverter::getSourceEncoding — Get the source encoding
  - UConverter::getSourceType — Get the source converter type
  - UConverter::getStandards — Get standards associated to converter names
  - UConverter::getSubstChars — Get substitution chars
  - UConverter::reasonText — Get string representation of the callback reason
  - UConverter::setDestinationEncoding — Set the destination encoding
  - UConverter::setSourceEncoding — Set the source encoding
  - UConverter::setSubstChars — Set the substitution chars
  - UConverter::toUCallback — Default "to" callback function
  - UConverter::transcode — Convert a string from one character encoding to another
- Grapheme 函数
  - grapheme_extract — Function to extract a sequence of default grapheme clusters from a text buffer, which must be encoded in UTF-8
  - grapheme_str_split — Split a string into an array
  - grapheme_stripos — Find position (in grapheme units) of first occurrence of a case-insensitive string
  - grapheme_stristr — Returns part of haystack string from the first occurrence of case-insensitive needle to the end of haystack
  - grapheme_strlen — Get string length in grapheme units
  - grapheme_strpos — Find position (in grapheme units) of first occurrence of a string
  - grapheme_strripos — Find position (in grapheme units) of last occurrence of a case-insensitive string
  - grapheme_strrpos — Find position (in grapheme units) of last occurrence of a string
  - grapheme_strstr — Returns part of haystack string from the first occurrence of needle to the end of haystack
  - grapheme_substr — Return part of a string
- IDN 函数
  - idn_to_ascii — 将域名转换为 IDNA ASCII 格式
  - idn_to_utf8 — 将域名从 IDNA ASCII 转换为 Unicode
- IntlChar
  - IntlChar::charAge — Get the "age" of the code point
  - IntlChar::charDigitValue — Get the decimal digit value of a decimal digit character
  - IntlChar::charDirection — Get bidirectional category value for a code point
  - IntlChar::charFromName — Find Unicode character by name and return its code point value
  - IntlChar::charMirror — Get the "mirror-image" character for a code point
  - IntlChar::charName — Retrieve the name of a Unicode character
  - IntlChar::charType — Get the general category value for a code point
  - IntlChar::chr — Return Unicode character by code point value
  - IntlChar::digit — Get the decimal digit value of a code point for a given radix
  - IntlChar::enumCharNames — Enumerate all assigned Unicode characters within a range
  - IntlChar::enumCharTypes — Enumerate all code points with their Unicode general categories
  - IntlChar::foldCase — Perform case folding on a code point
  - IntlChar::forDigit — Get character representation for a given digit and radix
  - IntlChar::getBidiPairedBracket — Get the paired bracket character for a code point
  - IntlChar::getBlockCode — Get the Unicode allocation block containing a code point
  - IntlChar::getCombiningClass — Get the combining class of a code point
  - IntlChar::getFC_NFKC_Closure — Get the FC_NFKC_Closure property for a code point
  - IntlChar::getIntPropertyMaxValue — Get the max value for a Unicode property
  - IntlChar::getIntPropertyMinValue — Get the min value for a Unicode property
  - IntlChar::getIntPropertyValue — Get the value for a Unicode property for a code point
  - IntlChar::getNumericValue — Get the numeric value for a Unicode code point
  - IntlChar::getPropertyEnum — Get the property constant value for a given property name
  - IntlChar::getPropertyName — Get the Unicode name for a property
  - IntlChar::getPropertyValueEnum — Get the property value for a given value name
  - IntlChar::getPropertyValueName — Get the Unicode name for a property value
  - IntlChar::getUnicodeVersion — Get the Unicode version
  - IntlChar::hasBinaryProperty — Check a binary Unicode property for a code point
  - IntlChar::isalnum — Check if code point is an alphanumeric character
  - IntlChar::isalpha — Check if code point is a letter character
  - IntlChar::isbase — Check if code point is a base character
  - IntlChar::isblank — Check if code point is a "blank" or "horizontal space" character
  - IntlChar::iscntrl — Check if code point is a control character
  - IntlChar::isdefined — Check whether the code point is defined
  - IntlChar::isdigit — Check if code point is a digit character
  - IntlChar::isgraph — Check if code point is a graphic character
  - IntlChar::isIDIgnorable — Check if code point is an ignorable character
  - IntlChar::isIDPart — Check if code point is permissible in an identifier
  - IntlChar::isIDStart — Check if code point is permissible as the first character in an identifier
  - IntlChar::isISOControl — Check if code point is an ISO control code
  - IntlChar::isJavaIDPart — Check if code point is permissible in a Java identifier
  - IntlChar::isJavaIDStart — Check if code point is permissible as the first character in a Java identifier
  - IntlChar::isJavaSpaceChar — Check if code point is a space character according to Java
  - IntlChar::islower — Check if code point is a lowercase letter
  - IntlChar::isMirrored — Check if code point has the Bidi_Mirrored property
  - IntlChar::isprint — Check if code point is a printable character
  - IntlChar::ispunct — Check if code point is punctuation character
  - IntlChar::isspace — Check if code point is a space character
  - IntlChar::istitle — Check if code point is a titlecase letter
  - IntlChar::isUAlphabetic — Check if code point has the Alphabetic Unicode property
  - IntlChar::isULowercase — Check if code point has the Lowercase Unicode property
  - IntlChar::isupper — Check if code point has the general category "Lu" (uppercase letter)
  - IntlChar::isUUppercase — Check if code point has the Uppercase Unicode property
  - IntlChar::isUWhiteSpace — Check if code point has the White_Space Unicode property
  - IntlChar::isWhitespace — Check if code point is a whitespace character according to ICU
  - IntlChar::isxdigit — Check if code point is a hexadecimal digit
  - IntlChar::ord — Return Unicode code point value of character
  - IntlChar::tolower — Make Unicode character lowercase
  - IntlChar::totitle — Make Unicode character titlecase
  - IntlChar::toupper — Make Unicode character uppercase
- IntlException — Exception class for intl errors
- IntlIterator — The IntlIterator class
  - IntlIterator::current — Get the current element
  - IntlIterator::key — Get the current key
  - IntlIterator::next — Move forward to the next element
  - IntlIterator::rewind — Rewind the iterator to the first element
  - IntlIterator::valid — Check if current position is valid
- intl 函数
  - intl_error_name — Get symbolic name for a given error code
  - intl_get_error_code — Get the last error code
  - intl_get_error_message — Get description of the last error
  - intl_is_failure — Check whether the given error code indicates failure

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