Simplified code.

module/VuFindDevTools/src/VuFindDevTools/Controller/DevtoolsController.php

@@ -114,14 +114,7 @@ class DevtoolsController extends \VuFind\Controller\AbstractBase
     protected function findMissingLanguageStrings($lang1, $lang2)
     {
         // Find strings missing from language 2:
-        $notInL2 = array();
-        $l2Keys = array_keys((array)$lang2);
-        foreach ($lang1 as $key => $junk) {
-            if (!in_array($key, $l2Keys)) {
-                $notInL2[] = $key;
-            }
-        }
-        return $notInL2;
+        return array_diff(array_keys((array)$lang1), array_keys((array)$lang2));
     }
 
     /**