Use PHP 8.5 styling for all release pages

Enables dark mode, syntax highlighting of variables, and unified design for all release pages. Release pages prior to 8.5 still lack the Key Features section.

Also fixed inconsistent i18n language spelling in the dropdowns on a few release pages, and corrected an English grammar typo on the PHP 8.1 page. No other content has been changed.

Author: theodorejb

releases/8.0/common.php

@@ -22,15 +22,22 @@
 ];
 
 function common_header(string $description): void {
-    global $MYSITE;
+    global $MYSITE, $lang;
 
     $meta_image_path = \htmlspecialchars(
         \filter_var($MYSITE . 'images/php8/php_8_released.png', \FILTER_VALIDATE_URL));
     $meta_description = \htmlspecialchars($description);
 
-    \site_header("PHP 8.0.0 Release Announcement", [
-        'current' => 'php8',
-        'css' => ['php8.css'],
+    $languages = [];
+    foreach (LANGUAGES as $code => $text) {
+        $languages[] = ['name' => $text, 'selected' => $lang === $code, 'url' => '/releases/8.0/' . $code . '.php'];
+    }
+
+    \site_header("PHP 8.0 Release Announcement", [
+        'current' => 'php85',
+        'css' => ['php85.css'],
+        'language_switcher' => $languages,
+        'theme_switcher' => true,
         'meta_tags' => <<<META
 <meta name="twitter:card" content="summary_large_image" />
 <meta name="twitter:site" content="@official_php" />
@@ -49,28 +56,7 @@ function common_header(string $description): void {
     ]);
 }
 
-function language_chooser(string $currentLang): void {
-    // Print out the form with all the options
-    echo '
-      <form action="" method="get" id="changelang" name="changelang">
-        <fieldset>
-          <label for="changelang-langs">Change language:</label>
-          <select onchange="location = this.value + \'.php\'" name="lang" id="changelang-langs">
-';
-
-    $tab = '            ';
-    foreach (LANGUAGES as $lang => $text) {
-        $selected = ($lang === $currentLang) ? ' selected="selected"' : '';
-        echo $tab, "<option value='$lang'$selected>$text</option>\n";
-    }
-
-    echo '          </select>
-        </fieldset>
-      </form>
-';
-}
-
-function message($code, $language = 'en')
+function message($code, $language = 'en'): string
 {
     $original = require __DIR__ . '/languages/en.php';
     if (($language !== 'en') && file_exists(__DIR__ . '/languages/' . $language . '.php')) {