Merge branch '4.4' into 5.0

* 4.4:
  Improved PHP-FPM section to list the common patterns to find a front controller
  fix displaying `empty_data` option for hidden field
  Improved tip message to make it more clear that the index.html takes precedence over the index.php
  Adds block about PHP-FPM behaviour

Author: javiereguiluz

reference/forms/types/hidden.rst

@@ -57,6 +57,12 @@ These options inherit from the :doc:`FormType </reference/forms/types/form>`:
 .. include:: /reference/forms/types/options/data.rst.inc
 
 .. include:: /reference/forms/types/options/empty_data.rst.inc
+    :end-before: DEFAULT_PLACEHOLDER
+
+The default value is ``''`` (the empty string).
+
+.. include:: /reference/forms/types/options/empty_data.rst.inc
+    :start-after: DEFAULT_PLACEHOLDER
 
 .. include:: /reference/forms/types/options/error_mapping.rst.inc
 

setup/symfony_server.rst

@@ -57,6 +57,24 @@ run the Symfony server in the background:
     # show the latest log messages
     $ symfony server:log
 
+Enabling PHP-FPM
+----------------
+
+When the server starts it will check for common patterns like ``web/app.php``,
+``web/app_dev.php`` or ``public/index.php``. If a file like this is found the
+server will automatically start with PHP-FPM enabled. Otherwise the server will
+start without PHP-FPM and will show a ``Page not found`` page when trying to 
+access a ``.php`` file in the browser.
+
+.. tip::
+
+    When an ``index.html`` and a front controller like e.g. ``index.php`` are
+    both present the server will still start with PHP-FPM enabled but the 
+    ``index.html`` will take precedence over the front controller. This means
+    when an ``index.html`` file is present in ``public`` or ``web``, it will be
+    displayed instead of the ``index.php`` which would show e.g. the Symfony
+    application.
+
 Enabling TLS
 ------------