The format for the xml string is the same that has to be returned by functions registered via calls to `xmlrpc_server_register_introspection_callback`.
It is documented at http://xmlrpc-epi.sourceforge.net/specs/rfc.system.describeMethods.php
(PHP 4 >= 4.1.0, PHP 5, PHP 7)
xmlrpc_parse_method_descriptions — 将 XML 译码成方法描述的列表
$xml
) : array此函数是实验性的。此函数的表象，包括名称及其相关文档都可能在未来的 PHP 发布版本中未通知就被修改。使用本函数风险自担。
本函数还未编写文档，仅有参数列表。
The format for the xml string is the same that has to be returned by functions registered via calls to `xmlrpc_server_register_introspection_callback`.
It is documented at http://xmlrpc-epi.sourceforge.net/specs/rfc.system.describeMethods.php