diff --git a/app/Config/Boot/development.php b/app/Config/Boot/development.php
index 05a86125..aa8099a4 100644
--- a/app/Config/Boot/development.php
+++ b/app/Config/Boot/development.php
@@ -7,6 +7,8 @@
  | In development, we want to show as many errors as possible to help
  | make sure they don't make it to production. And save us hours of
  | painful debugging.
+ |
+ | If you set 'display_errors' to '1', CI4's detailed error report will show.
  */
 error_reporting(-1);
 ini_set('display_errors', '1');
diff --git a/app/Config/Boot/production.php b/app/Config/Boot/production.php
index 21d25805..73c7c60a 100644
--- a/app/Config/Boot/production.php
+++ b/app/Config/Boot/production.php
@@ -6,6 +6,8 @@
  |--------------------------------------------------------------------------
  | Don't show ANY in production environments. Instead, let the system catch
  | it and display a generic error message.
+ |
+ | If you set 'display_errors' to '1', CI4's detailed error report will show.
  */
 ini_set('display_errors', '0');
 error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED & ~E_STRICT & ~E_USER_NOTICE & ~E_USER_DEPRECATED);
diff --git a/app/Config/Boot/testing.php b/app/Config/Boot/testing.php
index e07a1d43..e84670e9 100644
--- a/app/Config/Boot/testing.php
+++ b/app/Config/Boot/testing.php
@@ -1,5 +1,11 @@
 <?php
 
+/*
+ * The environment testing is reserved for PHPUnit testing. It has special
+ * conditions built into the framework at various places to assist with that.
+ * You can’t use it for your development.
+ */
+
 /*
  |--------------------------------------------------------------------------
  | ERROR DISPLAY
diff --git a/app/Config/Filters.php b/app/Config/Filters.php
index 8c02a4ac..41e76267 100644
--- a/app/Config/Filters.php
+++ b/app/Config/Filters.php
@@ -15,8 +15,9 @@ class Filters extends BaseConfig
      * Configures aliases for Filter classes to
      * make reading things nicer and simpler.
      *
-     * @var array<string, string>
-     * @phpstan-var array<string, class-string>
+     * @var array<string, array<int, string>|string> [filter_name => classname]
+     *                                               or [filter_name => [classname1, classname2, ...]]
+     * @phpstan-var array<string, class-string|list<class-string>>
      */
     public array $aliases = [
         'csrf'          => CSRF::class,
diff --git a/app/Views/errors/html/error_404.php b/app/Views/errors/html/error_404.php
index c3010132..e506f083 100644
--- a/app/Views/errors/html/error_404.php
+++ b/app/Views/errors/html/error_404.php
@@ -77,7 +77,7 @@
                 <?= nl2br(esc($message)) ?>
             <?php else : ?>
                 <?= lang('Errors.sorryCannotFind') ?>
-            <?php endif ?>
+            <?php endif; ?>
         </p>
     </div>
 </body>
diff --git a/app/Views/errors/html/error_exception.php b/app/Views/errors/html/error_exception.php
index f311d910..1c094d72 100644
--- a/app/Views/errors/html/error_exception.php
+++ b/app/Views/errors/html/error_exception.php
@@ -44,6 +44,7 @@
         <?php endif; ?>
     </div>
 
+    <?php if (defined('SHOW_DEBUG_BACKTRACE') && SHOW_DEBUG_BACKTRACE) : ?>
     <div class="container">
 
         <ul class="tabs" id="tabs">
@@ -66,7 +67,7 @@
                     <li>
                         <p>
                             <!-- Trace info -->
-                            <?php if (isset($row['file']) && is_file($row['file'])) :?>
+                            <?php if (isset($row['file']) && is_file($row['file'])) : ?>
                                 <?php
                                 if (isset($row['function']) && in_array($row['function'], ['include', 'include_once', 'require', 'require_once'], true)) {
                                     echo esc($row['function'] . ' ' . clean_path($row['file']));
@@ -375,6 +376,7 @@
         </div>  <!-- /tab-content -->
 
     </div> <!-- /container -->
+    <?php endif; ?>
 
     <div class="footer">
         <div class="container">
@@ -382,7 +384,8 @@
             <p>
                 Displayed at <?= esc(date('H:i:sa')) ?> &mdash;
                 PHP: <?= esc(PHP_VERSION) ?>  &mdash;
-                CodeIgniter: <?= esc(CodeIgniter::CI_VERSION) ?>
+                CodeIgniter: <?= esc(CodeIgniter::CI_VERSION) ?> --
+                Environment: <?= ENVIRONMENT ?>
             </p>
 
         </div>