docs: update sample code

Author: kenjis

user_guide_src/source/concepts/autoloader.rst

@@ -67,6 +67,7 @@ You may change this namespace by editing the **app/Config/Constants.php** file a
 new namespace value under the ``APP_NAMESPACE`` setting:
 
 .. literalinclude:: autoloader/002.php
+   :lines: 2-
 
 You will need to modify any existing files that are referencing the current namespace.
 

user_guide_src/source/concepts/autoloader/001.php

@@ -1,6 +1,16 @@
 <?php
 
-$psr4 = [
-    'App'         => APPPATH,
-    'CodeIgniter' => SYSTEMPATH,
-];
+namespace Config;
+
+use CodeIgniter\Config\AutoloadConfig;
+
+class Autoload extends AutoloadConfig
+{
+    // ...
+    public $psr4 = [
+        APP_NAMESPACE => APPPATH, // For custom app namespace
+        'Config'      => APPPATH . 'Config',
+    ];
+
+    // ...
+}

user_guide_src/source/concepts/autoloader/002.php

@@ -1,3 +1,3 @@
 <?php
 
-define('APP_NAMESPACE', 'App');
+defined('APP_NAMESPACE') || define('APP_NAMESPACE', 'App');

user_guide_src/source/concepts/autoloader/003.php

@@ -1,5 +1,15 @@
 <?php
 
-$classmap = [
-    'Markdown' => APPPATH . 'third_party/markdown.php',
-];
+namespace Config;
+
+use CodeIgniter\Config\AutoloadConfig;
+
+class Autoload extends AutoloadConfig
+{
+    // ...
+    public $classmap = [
+        'Markdown' => APPPATH . 'third_party/markdown.php',
+    ];
+
+    // ...
+}