PHP XML_Serializer bug

<?phprequire_once('XML/Serializer.php');define('XML_ATTR', 'XML_Attributes_Array');$options = array(    XML_SERIALIZER_OPTION_INDENT           => '  ',    XML_SERIALIZER_OPTION_LINEBREAKS       => "\n",    XML_SERIALIZER_OPTION_ROOT_NAME        => 'FooTag',    XML_SERIALIZER_OPTION_MODE             => XML_SERIALIZER_MODE_SIMPLEXML,    XML_SERIALIZER_OPTION_ATTRIBUTES_KEY   => XML_ATTR,    XML_SERIALIZER_OPTION_XML_ENCODING     => 'UTF-8',    XML_SERIALIZER_OPTION_XML_DECL_ENABLED => true,    XML_SERIALIZER_OPTION_ENTITIES         => XML_SERIALIZER_ENTITIES_XML,);$v = 'I say: "A", B & C, \'d\'!';$a = array('attr1' => $v);$xml = array(    XML_ATTR => $a,    'tag1' => array(XML_ATTR => $a, 'tag2' => $v),    'tag3' => array(XML_ATTR => $a, $v),);$serializer = new XML_Serializer($options);$serializer->serialize($xml);echo $serializer->getSerializedData();?>