Warning: require_once(XML/Serializer.php): failed to open stream: No such file or directory in /sites/aghdrive/var/pear/test/XML_Serializer/tests/Serializer_Option_CommentTest.php on line 11

Fatal error: require_once(): Failed opening required 'XML/Serializer.php' (include_path='.:/usr/local/lib/php') in /sites/aghdrive/var/pear/test/XML_Serializer/tests/Serializer_Option_CommentTest.php on line 11