sendsXml , expectsXml not found

[sicoa]

Greetings I have included the phar library but it does not include the sendsXml , expectsXml functions, although those are clearly stated in GET, PARSE, POST XML at the examples in the site http://phphttpclient.com/#install I get

Undefined function sendsXml 
Declaration of referenced function is not found in built-in library and project files.

What is the case here and how do i use httpful for xml? Thank you in advance