php-xml使用pear进行序列化和非序列化

我注意到PEAR XML_Serializer和XML_Unserializer是不"可逆"的，例如：

<?php
$a = array(1, 2);
$serializer = new XML_Serializer();
$serializer->serialize($a);
$b = $serializer->getSerializedData(); 
print($b); // "<array><XML_Serializer_Tag>1</Xml_Serializer_Tag><XML_Serializer_Tag>2</Xml_Serializer_Tag></array>"
$unserializer = new XML_Unserializer(); 
$unserializer->unserialize($b);
$c = $unserializer->getUnserializedData();
print_r($c); // array('XML_Serializer_Tag' => array(1, 2)) instead of array(1, 2)

XML_Unserializer是否有递归删除Xml_Serializer_Tag的选项？