docs: add comments in code

Author: kenjis

user_guide_src/source/tutorial/create_news_items/002.php

@@ -12,20 +12,22 @@ public function create()
     {
         helper('form');
 
+        // Checks whether the form is submitted.
         if (strtolower($this->request->getMethod()) !== 'post') {
-            // Returns the form.
+            // The form is not submitted, so returns the form.
             return view('templates/header', ['title' => 'Create a news item'])
                 . view('news/create')
                 . view('templates/footer');
         }
 
         $post = $this->request->getPost(['title', 'body']);
 
+        // Checks whether the submitted data passed the validation rules.
         if (! $this->validateData($post, [
             'title' => 'required|min_length[3]|max_length[255]',
             'body'  => 'required|min_length[10]|max_length[5000]',
         ])) {
-            // Returns the form.
+            // The validation fails, so returns the form.
             return view('templates/header', ['title' => 'Create a news item'])
                 . view('news/create')
                 . view('templates/footer');