docs: add note for Validation::withRequest()

Author: kenjis

user_guide_src/source/incoming/incomingrequest.rst

@@ -80,6 +80,8 @@ With CodeIgniter's built-in methods you can simply do this:
 
 .. literalinclude:: incomingrequest/008.php
 
+.. _incomingrequest-getting-data:
+
 Getting Data
 ============
 
@@ -103,6 +105,8 @@ maintaining the ability to control the order you look for it:
 * ``$request->getPostGet()`` - checks ``$_POST`` first, then ``$_GET``
 * ``$request->getGetPost()`` - checks ``$_GET`` first, then ``$_POST``
 
+.. _incomingrequest-getting-json-data:
+
 Getting JSON Data
 =================
 
@@ -138,6 +142,8 @@ correct ``Content-Type`` header.
 
 .. note:: See the documentation for :php:func:`dot_array_search()` in the ``Array`` helper for more information on "dot" notation.
 
+.. _incomingrequest-retrieving-raw-data:
+
 Retrieving Raw Data (PUT, PATCH, DELETE)
 ========================================
 

user_guide_src/source/libraries/validation.rst

@@ -286,6 +286,15 @@ data to be validated:
 
 .. literalinclude:: validation/008.php
 
+.. note:: This method gets JSON data from
+    :ref:`$request->getJSON() <incomingrequest-getting-json-data>`
+    when the request is a JSON request (``Content-Type: application/json``),
+    or gets Raw data from
+    :ref:`$request->getRawInput() <incomingrequest-retrieving-raw-data>`
+    when the request is a PUT, PATCH, DELETE request and
+    is not HTML form post (``Content-Type: multipart/form-data``),
+    or gets data from :ref:`$request->getVar() <incomingrequest-getting-data>`.
+
 Working with Validation
 ***********************