答案：PHP的intl擴(kuò)展基于ICU庫實(shí)現(xiàn)國際化，支持多語言格式化、翻譯和排序。首先安裝并啟用intl擴(kuò)展，Linux系統(tǒng)使用apt-get或yum安裝，Windows在php.ini中開啟extension=intl。通過NumberFormatter按地區(qū)格式化數(shù)字，如de_DE輸出1.234.567,89；IntlDateFormatter處理日期顯示，如fr_FR顯示“l(fā)undi 4 septembre 2023”；CurrencyFormatter格式化貨幣，en_US顯示$99.99。MessageFormatter支持帶占位符的翻譯，自動處理復(fù)數(shù)和語法，如es_ES將2映射為“2 libros”。Collator類按語言規(guī)則排序，sv_SE正確排列瑞典語字符順序。使用Locale::acceptFromHttp從HTTP頭檢測用戶語言，或設(shè)默認(rèn)locale如fr_FR，多數(shù)類會自動繼承。只需啟用擴(kuò)展，選擇合適類并傳入locale即可實(shí)現(xiàn)全球化功能。

The intl extension in PHP provides powerful tools for internationalization (i18n), allowing your applications to handle multiple languages, formats, and regional settings. It's built on top of the ICU (International Components for Unicode) library and supports features like locale-aware formatting, message translation, collation, and more. Here’s how to use it effectively.

Install and Enable the intl Extension

Before using intl, make sure it’s installed and enabled in your PHP environment.

Format Dates, Numbers, and Currencies by Locale

The intl extension includes classes like NumberFormatter, IntlDateFormatter, and CurrencyFormatter to display data according to user locale.

Format numbers:

$formatter = new NumberFormatter('de_DE', NumberFormatter::DECIMAL);
echo $formatter->format(1234567.89); // Output: 1.234.567,89

Format dates:

$formatter = new IntlDateFormatter(
    'fr_FR',
    IntlDateFormatter::FULL,
    IntlDateFormatter::NONE,
    'Europe/Paris'
);
echo $formatter->format(time());
// Output: lundi 4 septembre 2023

Format currency:

$formatter = new NumberFormatter('en_US', NumberFormatter::CURRENCY);
echo $formatter->formatCurrency(99.99, 'USD'); // $99.99

Translate Messages Using MessageFormatter

Use MessageFormatter to support dynamic, localized messages with placeholders.

$message = "{0, plural, one {# book} other {# books}}";
$formatter = new MessageFormatter('es_ES', $message);
echo $formatter->format([2]); // "2 libros"

This handles pluralization and grammar rules per language automatically. You can also use named arguments and select clauses for gender or categories.

Sort Strings According to Locale (Collator)

Standard string sorting may not respect language-specific rules. Use Collator for accurate sorting.

$collator = new Collator('sv_SE'); // Swedish
$words = ['zoo', '?tta', '?pple', '?r'];
$collator->asort($words);
print_r($words); // Correct Swedish order: ?pple, ?r, ?tta, zoo

Without Collator, sorting would be based on ASCII values and incorrect for many languages.

Detect and Set Default Locale

You can detect user locale from HTTP headers or set a default for your app.

// Get best match from browser Accept-Language
$locale = Locale::acceptFromHttp($_SERVER['HTTP_ACCEPT_LANGUAGE'] ?? 'en');
setlocale(LC_ALL, $locale);
<p>// Or set manually
Locale::setDefault('fr_FR');</p>

Many intl classes use the default locale if none is specified.

Basically just enable intl, pick the right formatter or collator, and pass the correct locale. It handles the rest—no need to reinvent date formats or sort rules for every language.

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