feature #6590 Added note on YAML mappings as objects (dantleech)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes #6590).

Discussion
----------

Added note on YAML mappings as objects

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | 2.7 > 3.0

Depends on #6582

Commits
-------

e9de4ca Added note on YAML mappings as objects

Author: xabbuh

components/yaml/introduction.rst

@@ -148,6 +148,20 @@ error if something goes wrong by adding the filename to the message.
 
 .. _components-yaml-dump:
 
+Objects for Mappings
+....................
+
+.. versionadded:: 2.7
+    Support for parsing mappings as objects was introduced in Symfony 2.6.
+
+Yaml :ref:`mappings <yaml-format-collections>` are basically associative
+arrays. You can instruct the parser to return mappings as objects (i.e.
+``\stdClass`` instances) by setting the fourth argument to ``true``::
+
+    $object = Yaml::parse('{"foo": "bar"}', false, false, true);
+    echo get_class($object); // stdClass
+    echo $object->foo; // bar
+
 Writing YAML Files
 ~~~~~~~~~~~~~~~~~~
 

components/yaml/yaml_format.rst

@@ -165,6 +165,8 @@ YAML uses the ISO-8601 standard to express dates:
     # simple date
     2002-12-14
 
+.. _yaml-format-collections:
+
 Collections
 -----------