docs: add sample code with variable-length argument lists

For multiple URI segments matched a placeholder.

Author: kenjis

user_guide_src/source/incoming/routing.rst

@@ -200,11 +200,19 @@ For example the route:
 
 will match **product/123**, **product/123/456**, **product/123/456/789** and so on.
 
+In the above example, if the ``$1`` placeholder contains a slash
+(``/``), it will still be split into multiple parameters when passed to
+``Catalog::productLookup()``.
+
 The implementation in the
 Controller should take into account the maximum parameters:
 
 .. literalinclude:: routing/011.php
 
+Or you can use `variable-length argument lists <https://www.php.net/manual/en/functions.arguments.php#functions.variable-arg-list>`_:
+
+.. literalinclude:: routing/068.php
+
 .. important:: Do not put any placeholder after ``(:any)``. Because the number of
     parameters passed to the controller method may change.
 
@@ -249,6 +257,10 @@ redirect them back to the same page after they log in, you may find this example
 
 .. literalinclude:: routing/019.php
 
+In the above example, if the ``$1`` placeholder contains a slash
+(``/``), it will still be split into multiple parameters when passed to
+``Auth::login()``.
+
 For those of you who don't know regular expressions and want to learn more about them,
 `regular-expressions.info <https://www.regular-expressions.info/>`_ might be a good starting point.
 

user_guide_src/source/incoming/routing/068.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace App\Controllers;
+
+class Catalog extends BaseController
+{
+    public function productLookup(...$params)
+    {
+        echo $params[0] ?? null; // Will be 123 in all examples
+        echo $params[1] ?? null; // null in first, 456 in second and third example
+        echo $params[2] ?? null; // null in first and second, 789 in third
+    }
+}