Fixed typo for YamlEncoder section

Minor typo fix for YamlEncoder section

Author: vertisan

components/serializer.rst

@@ -994,7 +994,7 @@ The ``YamlEncoder`` Context Options
 The ``encode()`` method, like other encoder, uses ``context`` to set
 configuration options for the YamlEncoder an associative array::
 
-    $xmlEncoder->encode($array, 'xml', $context);
+    $yamlEncoder->encode($array, 'yaml', $context);
 
 These are the options available: