Merge pull request #7560 from kenjis/fix-docs-routing.rst

docs: improve Array Callable Syntax explanation in routing.rst

Author: kenjis

user_guide_src/source/incoming/routing.rst

@@ -85,7 +85,9 @@ Specifying Route Handlers
 Controller's Namespace
 ----------------------
 
-If a controller name is stated without beginning with ``\``, the :ref:`routing-default-namespace` will be prepended:
+When you specify a controller and method name as a string, if a controller is
+written without a leading ``\``, the :ref:`routing-default-namespace` will be
+prepended:
 
 .. literalinclude:: routing/063.php
 
@@ -114,6 +116,17 @@ Or using ``use`` keyword:
 .. literalinclude:: routing/014.php
    :lines: 2-
 
+If you forget to add ``use App\Controllers\Home;``, the controller classname is
+interpreted as ``Config\Home``, not ``App\Controllers\Home`` because
+**app/Config/Routes.php** has ``namespace Config;`` at the top.
+
+.. note:: When you use Array Callable Syntax, the classname is always interpreted
+    as a fully qualified classname. So :ref:`routing-default-namespace` and
+    :ref:`namespace option <assigning-namespace>` have no effect.
+
+Array Callable Syntax and Placeholders
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 If there are placeholders, it will automatically set the parameters in the specified order:
 
 .. literalinclude:: routing/015.php