Case insensitive comparison.

src/Utility/Language.php

@@ -116,8 +116,8 @@ class Language {
 	 * @return float
 	 */
 	protected static function _matchLanguage($a, $b) {
-		$a = explode('-', $a);
-		$b = explode('-', $b);
+		$a = explode('-', strtolower($a));
+		$b = explode('-', strtolower($b));
 
 		for ($i = 0, $n = min(count($a), count($b)); $i < $n; $i++) {
 			if ($a[$i] !== $b[$i]) {

tests/TestCase/Utility/LanguageTest.php

@@ -49,7 +49,7 @@ class LanguageTest extends TestCase {
 			]
 		];
 		$this->assertSame($expected, $res);
-		
+
 		$res = Language::parseLanguageList($_SERVER['HTTP_ACCEPT_LANGUAGE'], false);
 		$expected = [
 			'1.0' => [
@@ -94,7 +94,7 @@ class LanguageTest extends TestCase {
 		];
 		$this->assertSame($expected, $res);
 
-		$res = Language::findMatches(['de']);
+		$res = Language::findMatches(['DE']);
 		$expected = [
 			'1.0' => [
 				'de-de'