diff --git a/docs.php b/docs.php
index 04dd13107..3119d5bf7 100644
--- a/docs.php
+++ b/docs.php
@@ -1,4 +1,7 @@
 <?php
+
+use phpweb\I18n\Languages;
+
 $_SERVER['BASE_PAGE'] = 'docs.php';
 include_once __DIR__ . '/include/prepend.inc';
 
@@ -27,19 +30,19 @@ site_header("Documentation", ["current" => "docs"]);
 <?php
 
 // List all manual languages viewable online
-$lastlang = end($ACTIVE_ONLINE_LANGUAGES);
-foreach ($ACTIVE_ONLINE_LANGUAGES as $langcode => $langname) {
+$lastlang = array_key_last(Languages::ACTIVE_ONLINE_LANGUAGES);
+foreach (Languages::ACTIVE_ONLINE_LANGUAGES as $langcode => $langname) {
     if (!file_exists($_SERVER["DOCUMENT_ROOT"] . "/manual/{$langcode}/index.php")) {
         continue;
     }
 
     // Make preferred language bold
-    if ($langcode == $LANG) { echo "<strong>"; }
+    if ($langcode === $LANG) { echo "<strong>"; }
 
     echo '<a href="/manual/' . $langcode . '/">' . $langname . '</a>';
-    echo ($lastlang != $langname) ? ",\n" : "\n";
+    echo ($lastlang !== $langcode) ? ",\n" : "\n";
 
-    if ($langcode == $LANG) { echo "</strong>"; }
+    if ($langcode === $LANG) { echo "</strong>"; }
 }
 
 ?>
diff --git a/download-docs.php b/download-docs.php
index 0d31fd10f..9abfc80f5 100644
--- a/download-docs.php
+++ b/download-docs.php
@@ -1,9 +1,12 @@
 <?php
+
+use phpweb\I18n\Languages;
+
 $_SERVER['BASE_PAGE'] = 'download-docs.php';
 include_once __DIR__ . '/include/prepend.inc';
 
 if (!empty($_GET['active_langs'])) {
-    echo serialize($ACTIVE_ONLINE_LANGUAGES);
+    echo serialize(Languages::ACTIVE_ONLINE_LANGUAGES);
     exit;
 }
 
@@ -90,8 +93,8 @@ $files = []; $found_formats = [];
 $filepath = $filename = '';
 
 // Go through all possible manual languages
-foreach ($LANGUAGES as $langcode => $language) {
-    if (isset($INACTIVE_ONLINE_LANGUAGES[$langcode]) && $MYSITE !== 'http://docs.php.net/') {
+foreach (Languages::LANGUAGES as $langcode => $language) {
+    if (isset(Languages::INACTIVE_ONLINE_LANGUAGES[$langcode]) && $MYSITE !== 'http://docs.php.net/') {
        continue;
     }
 
@@ -180,7 +183,7 @@ if (count($found_formats) == 0) {
             $cellclass = "";
         }
 
-        echo "<tr>\n<th class=\"subl\">" . $LANGUAGES[$langcode] . "</th>\n";
+        echo "<tr>\n<th class=\"subl\">" . Languages::LANGUAGES[$langcode] . "</th>\n";
 
         foreach ($formats as $formatname => $extension) {
 
diff --git a/error.php b/error.php
index 2801188f1..423135a29 100644
--- a/error.php
+++ b/error.php
@@ -9,11 +9,11 @@
 
 */
 
+use phpweb\I18n\Languages;
 use phpweb\UserPreferences;
 
 // Ensure that our environment is set up
 include_once __DIR__ . '/include/prepend.inc';
-include_once __DIR__ . '/include/languages.inc';
 include_once __DIR__ . '/include/errors.inc';
 
 // Get URI for this request, strip leading slash
@@ -79,7 +79,7 @@ if (preg_match("!(.*\\.php)3$!", $URI, $array)) {
 //     default language manual accessibility on mirror sites through /manual/filename)
 // @todo do we rely on this? how about removing it...
 if (preg_match("!^manual/([^/]*)$!", $URI, $array)) {
-    if (!isset($INACTIVE_ONLINE_LANGUAGES[$array[1]])) {
+    if (!isset(Languages::INACTIVE_ONLINE_LANGUAGES[$array[1]])) {
         mirror_redirect("/manual/$LANG/$array[1]");
     }
 } elseif (preg_match("!^manual/html/([^/]+)$!", $URI, $array)) {
@@ -705,10 +705,10 @@ if (preg_match("!^manual/(.+)/function\.(.+)-(.+).php$!", $URI, $array)) {
 // ============================================================================
 // For manual pages for inactive languages, point visitors to the English page
 if (preg_match("!^manual/([^/]+)/([^/]+).php$!", $URI, $match) &&
-    isset($INACTIVE_ONLINE_LANGUAGES[$match[1]])) {
+    isset(Languages::INACTIVE_ONLINE_LANGUAGES[$match[1]])) {
     $try = find_manual_page("en", $match[2]);
     if ($try) {
-        error_inactive_manual_page($INACTIVE_ONLINE_LANGUAGES[$match[1]], $try);
+        error_inactive_manual_page(Languages::INACTIVE_ONLINE_LANGUAGES[$match[1]], $try);
     }
 }
 
diff --git a/include/errors.inc b/include/errors.inc
index 17fd86912..76637c2da 100644
--- a/include/errors.inc
+++ b/include/errors.inc
@@ -5,6 +5,8 @@
   not available.
 */
 
+use phpweb\I18n\Languages;
+
 // A 'good looking' 404 error message page
 function error_404(): void
 {
@@ -37,7 +39,7 @@ function error_404_manual(): void
 // An error message page for manual pages from inactive languages
 function error_inactive_manual_page($lang_name, $en_page): void
 {
-    global $MYSITE, $ACTIVE_ONLINE_LANGUAGES;
+    global $MYSITE;
     status_header(404);
     site_header('Page gone', ["noindex"]);
     echo "<h1>Page gone</h1>\n" .
@@ -48,7 +50,7 @@ function error_inactive_manual_page($lang_name, $en_page): void
     echo "<p>The English page is available at <a href=\"{$en_url}\">{$en_url}</a></p>\n";
     echo "<p>Several other languages are also available:</p>\n";
     echo "<ul>\n";
-    foreach ($ACTIVE_ONLINE_LANGUAGES as $alt_lang => $alt_lang_name) {
+    foreach (Languages::ACTIVE_ONLINE_LANGUAGES as $alt_lang => $alt_lang_name) {
         if ($alt_lang === "en") {
             continue;
         }
diff --git a/include/langchooser.inc b/include/langchooser.inc
index 61def940f..f46498a36 100644
--- a/include/langchooser.inc
+++ b/include/langchooser.inc
@@ -28,6 +28,7 @@
 
 */
 
+use phpweb\I18n\Languages;
 use phpweb\LangChooser;
 
 require_once __DIR__ . '/../src/autoload.php';
@@ -37,7 +38,7 @@ $_SERVER['STRIPPED_URI'] = htmlspecialchars($_SERVER['REQUEST_URI'], ENT_QUOTES,
 
 // The code is encapsulated in a function,
 // so the variable namespace is not polluted
-list($LANG, $EXPL_LANG) = (new LangChooser($LANGUAGES, $INACTIVE_ONLINE_LANGUAGES, $userPreferences->languageCode, default_language() ?: ''))->chooseCode(
+list($LANG, $EXPL_LANG) = (new LangChooser(Languages::LANGUAGES, Languages::INACTIVE_ONLINE_LANGUAGES, $userPreferences->languageCode, default_language() ?: ''))->chooseCode(
     $_REQUEST['lang'] ?? null,
     $_SERVER['REQUEST_URI'],
     $_SERVER['HTTP_ACCEPT_LANGUAGE'] ?? null,
diff --git a/include/languages.inc b/include/languages.inc
index e19726371..84e97b8c2 100644
--- a/include/languages.inc
+++ b/include/languages.inc
@@ -1,9 +1,9 @@
 <?php
+/**
+ * This file is deprecated, and it exists for backward compatibility purposes only.
+ * It must be kept in sync with {@see \phpweb\I18n\Languages}.
+ */
 
-/*
- This is a list of all manual languages hosted
- within PHP Git repositories (https://github.com/php/doc-{lang})
-*/
 $LANGUAGES = [
     'en' => 'English',
     'de' => 'German',
@@ -20,32 +20,9 @@ $LANGUAGES = [
     'zh' => 'Chinese (Simplified)',
 ];
 
-/*
- The following languages are inactive, which means they will not:
- - Show up via the language select box at php.net
- - Be selectable via my.php
- - Accept redirections to the translation, despite ACCEPT_LANGUAGE
- - Be listed at php.net/docs or php.net/download-docs
- However, translation status for these languages is available at:
- - https://doc.php.net/
-*/
 $INACTIVE_ONLINE_LANGUAGES = [
     'pl' => 'Polish',
     'ro' => 'Romanian',
 ];
 
 $ACTIVE_ONLINE_LANGUAGES = array_diff($LANGUAGES, $INACTIVE_ONLINE_LANGUAGES);
-
-// Convert between language codes back and forth
-// [We use non-standard languages codes and so conversion
-// is needed when communicating with the outside world]
-function language_convert(string $langcode): string
-{
-    global $LANGUAGES;
-    switch ($langcode) {
-        case 'zh_cn': return 'zh';
-        default:
-            // Fallback on english if we got something wacky
-            return array_key_exists($langcode, $LANGUAGES) ? $langcode : 'en';
-    }
-}
diff --git a/include/layout.inc b/include/layout.inc
index 5174395e4..86969807e 100644
--- a/include/layout.inc
+++ b/include/layout.inc
@@ -1,5 +1,6 @@
 <?php
 
+use phpweb\I18n\Languages;
 use phpweb\Navigation\NavItem;
 
 $_SERVER['STATIC_ROOT'] = $MYSITE;
@@ -463,7 +464,7 @@ META
 
     $config["headsup"] = get_news_changes();
 
-    $lang = language_convert($config["lang"]);
+    $lang = (new Languages())->convert($config["lang"]);
     $curr = $config["current"];
     $classes = $config['classes'];
 
diff --git a/include/shared-manual.inc b/include/shared-manual.inc
index 8610f112f..eb0437e27 100644
--- a/include/shared-manual.inc
+++ b/include/shared-manual.inc
@@ -22,6 +22,7 @@ $PGI = []; $SIDEBAR_DATA = '';
 // User note display functions
 // =============================================================================
 
+use phpweb\I18n\Languages;
 use phpweb\UserNotes\Sorter;
 use phpweb\UserNotes\UserNote;
 
@@ -271,7 +272,6 @@ function manual_navigation_methodname($methodname) {
 // including HTTP header information
 function manual_setup($setup): void {
     global $PGI, $MYSITE, $USERNOTES;
-    global $ACTIVE_ONLINE_LANGUAGES;
 
     //TODO: get rid of this hack to get the related items into manual_footer
     global $__RELATED;
@@ -281,7 +281,7 @@ function manual_setup($setup): void {
     }
     $PGI = $setup;
     // Set base href for this manual page
-    $base = 'manual/' . language_convert($setup['head'][1]) . "/";
+    $base = 'manual/' . (new Languages())->convert($setup['head'][1]) . "/";
     $_SERVER['BASE_PAGE'] = $base . $setup['this'][0];
     $_SERVER['BASE_HREF'] = $MYSITE . $_SERVER['BASE_PAGE'];
 
@@ -313,7 +313,7 @@ function manual_setup($setup): void {
     $config = [
         "current" => "docs",
         "breadcrumbs" => $breadcrumbs,
-        "languages" => array_keys($ACTIVE_ONLINE_LANGUAGES),
+        "languages" => array_keys(Languages::ACTIVE_ONLINE_LANGUAGES),
         "meta-navigation" => [
             "contents" => $base . $setup["home"][0],
             "index" => $base . $setup["up"][0],
@@ -340,12 +340,12 @@ PAGE_TOOLS;
 }
 
 function manual_language_chooser($currentlang, $currentpage) {
-    global $ACTIVE_ONLINE_LANGUAGES, $LANG;
+    global $LANG;
 
     // Prepare the form with all the options
     $othersel = ' selected="selected"';
     $out = [];
-    foreach ($ACTIVE_ONLINE_LANGUAGES as $lang => $text) {
+    foreach (Languages::ACTIVE_ONLINE_LANGUAGES as $lang => $text) {
         $selected = '';
         if ($lang == $currentlang) {
             $selected = ' selected="selected"';
diff --git a/include/site.inc b/include/site.inc
index 50877ecbf..2aa9c4a59 100644
--- a/include/site.inc
+++ b/include/site.inc
@@ -1,5 +1,7 @@
 <?php
 
+use phpweb\I18n\Languages;
+
 // Define some constants, and $MIRRORS array
 // Mirror type constants
 const MIRROR_DOWNLOAD = 0;
@@ -31,9 +33,6 @@ $MIRRORS = [
  */
 $COUNTRIES = include __DIR__ . '/countries.inc';
 
-// Define $LANGUAGES array
-include __DIR__ . '/languages.inc';
-
 // Returns true if the current (or specified)
 // site is the primary mirror site
 function is_primary_site($site = false)
@@ -261,14 +260,14 @@ if (!isset($MIRRORS[$MYSITE])) {
 
 // Override mirror language with local preference
 if (isset($_SERVER['MIRROR_LANGUAGE'])) {
-    if (isset($LANGUAGES[$_SERVER['MIRROR_LANGUAGE']])) {
+    if (isset(Languages::LANGUAGES[$_SERVER['MIRROR_LANGUAGE']])) {
         $MIRRORS[$MYSITE][6] = $_SERVER['MIRROR_LANGUAGE'];
     }
 }
 
 // Fallback to English in case the language
 // set is definitely not supported
-if (!isset($LANGUAGES[$MIRRORS[$MYSITE][6]])) {
+if (!isset(Languages::LANGUAGES[$MIRRORS[$MYSITE][6]])) {
     $MIRRORS[$MYSITE][6] = "en";
 }
 
diff --git a/js/search-index.php b/js/search-index.php
index 6fb15b3cb..7d2f50193 100644
--- a/js/search-index.php
+++ b/js/search-index.php
@@ -1,5 +1,7 @@
 <?php
 
+use phpweb\I18n\Languages;
+
 $_GET["lang"] = "en";
 if (!isset($_GET["lang"])) {
     header("Location: http://php.net");
@@ -9,7 +11,7 @@ if (empty($_SERVER["DOCUMENT_ROOT"])) {
     $_SERVER["DOCUMENT_ROOT"] = __DIR__ . "/../";
 }
 include __DIR__ . '/../include/prepend.inc';
-if (!isset($ACTIVE_ONLINE_LANGUAGES[$_GET["lang"]])) {
+if (!isset(Languages::ACTIVE_ONLINE_LANGUAGES[$_GET["lang"]])) {
     header("Location: http://php.net");
 }
 $lang = $_GET["lang"];
diff --git a/manual/help-translate.php b/manual/help-translate.php
index ab8b5c051..df69f428d 100644
--- a/manual/help-translate.php
+++ b/manual/help-translate.php
@@ -1,4 +1,7 @@
 <?php
+
+use phpweb\I18n\Languages;
+
 $_SERVER['BASE_PAGE'] = 'manual/help-translate.php';
 include_once __DIR__ . '/../include/prepend.inc';
 include_once __DIR__ . '/../include/shared-manual.inc';
@@ -26,7 +29,7 @@ The following list of languages already contain SVN modules, and will show up on
 // $archived are manuals we have old versions of
 $archived = ['da', 'kr', 'pl', 'tw'];
 
-foreach ($INACTIVE_ONLINE_LANGUAGES as $cc => $lang) {
+foreach (Languages::INACTIVE_ONLINE_LANGUAGES as $cc => $lang) {
     $link = 'no archive';
     if (in_array($cc, $archived, true)) {
         $link = '<a href="http://docs.php.net/manual/' . $cc . '">archive</a>';
diff --git a/mirror.php b/mirror.php
index ea1c397d6..4b6c40dd2 100644
--- a/mirror.php
+++ b/mirror.php
@@ -1,4 +1,7 @@
 <?php
+
+use phpweb\I18n\Languages;
+
 $_SERVER['BASE_PAGE'] = 'mirror.php';
 include_once __DIR__ . '/include/prepend.inc';
 $SIDEBAR_DATA = '
@@ -84,7 +87,7 @@ site_header("Information About This PHP Mirror Site", ["current" => "community"]
 <h2>Mirror Services</h2>
 
 <ul>
- <li>Default language is <?php echo $LANGUAGES[default_language()]; ?></li>
+ <li>Default language is <?php echo Languages::LANGUAGES[default_language()]; ?></li>
 </ul>
 
 <h2>Mirror Status</h2>
diff --git a/my.php b/my.php
index 8ad08ded4..1fdb9d282 100644
--- a/my.php
+++ b/my.php
@@ -1,5 +1,6 @@
 <?php
 
+use phpweb\I18n\Languages;
 use phpweb\UserPreferences;
 
 $_SERVER['BASE_PAGE'] = 'my.php';
@@ -9,7 +10,7 @@ include_once __DIR__ . '/include/prepend.inc';
 header_nocache();
 
 // Languages array copy and options to list
-$langs = $ACTIVE_ONLINE_LANGUAGES;
+$langs = Languages::ACTIVE_ONLINE_LANGUAGES;
 $options = [];
 
 // We have post data, and it is an available language
diff --git a/src/I18n/Languages.php b/src/I18n/Languages.php
new file mode 100644
index 000000000..a74fc6546
--- /dev/null
+++ b/src/I18n/Languages.php
@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace phpweb\I18n;
+
+use function array_key_exists;
+
+final class Languages
+{
+    /**
+     * This is a list of all manual languages hosted
+     * within PHP Git repositories (https://github.com/php/doc-{lang})
+     */
+    public const LANGUAGES = [
+        'en' => 'English',
+        'de' => 'German',
+        'es' => 'Spanish',
+        'fr' => 'French',
+        'it' => 'Italian',
+        'ja' => 'Japanese',
+        'pl' => 'Polish',
+        'pt_BR' => 'Brazilian Portuguese',
+        'ro' => 'Romanian',
+        'ru' => 'Russian',
+        'tr' => 'Turkish',
+        'uk' => 'Ukrainian',
+        'zh' => 'Chinese (Simplified)',
+    ];
+
+    /**
+     * The following languages are inactive, which means they will not:
+     * - Show up via the language select box at php.net
+     * - Be selectable via my.php
+     * - Accept redirections to the translation, despite ACCEPT_LANGUAGE
+     * - Be listed at php.net/docs or php.net/download-docs
+     * However, translation status for these languages is available at:
+     * - https://doc.php.net/
+     */
+    public const INACTIVE_ONLINE_LANGUAGES = [
+        'pl' => 'Polish',
+        'ro' => 'Romanian',
+    ];
+
+    public const ACTIVE_ONLINE_LANGUAGES = [
+        'en' => 'English',
+        'de' => 'German',
+        'es' => 'Spanish',
+        'fr' => 'French',
+        'it' => 'Italian',
+        'ja' => 'Japanese',
+        'pt_BR' => 'Brazilian Portuguese',
+        'ru' => 'Russian',
+        'tr' => 'Turkish',
+        'uk' => 'Ukrainian',
+        'zh' => 'Chinese (Simplified)',
+    ];
+
+    /**
+     * Convert between language codes back and forth
+     *
+     * Uses non-standard languages codes and so conversion is needed when communicating with the outside world.
+     *
+     * Fall back to English if the language is not available.
+     */
+    public function convert(string $languageCode): string
+    {
+        return match ($languageCode) {
+            'zh_cn', 'zh_CN' => 'zh',
+            'pt_br', 'pt_BR' => 'pt_BR',
+            default => array_key_exists($languageCode, self::LANGUAGES) ? $languageCode : 'en',
+        };
+    }
+}
diff --git a/tests/Unit/I18n/LanguagesTest.php b/tests/Unit/I18n/LanguagesTest.php
new file mode 100644
index 000000000..c1eeacd72
--- /dev/null
+++ b/tests/Unit/I18n/LanguagesTest.php
@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+namespace phpweb\Test\Unit\I18n;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use phpweb\I18n\Languages;
+
+use function array_diff;
+
+#[CoversClass(Languages::class)]
+final class LanguagesTest extends TestCase
+{
+    #[DataProvider('languageCodeProvider')]
+    public function testConvert(string $languageCode, string $expected): void
+    {
+        self::assertSame($expected, (new Languages())->convert($languageCode));
+    }
+
+    public static function languageCodeProvider(): iterable
+    {
+        yield ['en', 'en'];
+        yield ['de', 'de'];
+        yield ['es', 'es'];
+        yield ['fr', 'fr'];
+        yield ['it', 'it'];
+        yield ['ja', 'ja'];
+        yield ['pl', 'pl'];
+        yield ['pt_br', 'pt_BR'];
+        yield ['pt_BR', 'pt_BR'];
+        yield ['ro', 'ro'];
+        yield ['ru', 'ru'];
+        yield ['tr', 'tr'];
+        yield ['uk', 'uk'];
+        yield ['zh', 'zh'];
+        yield ['zh_cn', 'zh'];
+        yield ['zh_CN', 'zh'];
+        yield ['unknown', 'en'];
+        yield ['', 'en'];
+    }
+
+    public function testConstantsDifference(): void
+    {
+        self::assertSame(
+            array_diff(Languages::LANGUAGES, Languages::INACTIVE_ONLINE_LANGUAGES),
+            Languages::ACTIVE_ONLINE_LANGUAGES,
+        );
+    }
+
+    public function testLanguagesIncGlobalVariables(): void
+    {
+        global $LANGUAGES, $INACTIVE_ONLINE_LANGUAGES, $ACTIVE_ONLINE_LANGUAGES;
+
+        include __DIR__ . '/../../../include/languages.inc';
+
+        self::assertSame(Languages::LANGUAGES, $LANGUAGES);
+        self::assertSame(Languages::INACTIVE_ONLINE_LANGUAGES, $INACTIVE_ONLINE_LANGUAGES);
+        self::assertSame(Languages::ACTIVE_ONLINE_LANGUAGES, $ACTIVE_ONLINE_LANGUAGES);
+    }
+}