How does the PHP file display the XML-style file and how is it done?

How does the PHP file display XML-style files, and how is it done??
First of all, not outside the chain.
Where to use the API, there is an example, http://tuan.cctcct.com/interface/xml/team_list.asp
It feels strange, how does his ASP show up as XML? How can PHP do this?
There are many lists in this file, take one of them: http://tuan.cctcct.com/interface/xml/team_detail.asp?team_id=1562
Next to the ID can be generated directly, do not need to generate an XML file for each, so much more convenient.
Thank you, sir.
------to solve the idea----------------------

Header (' Content-type:text/xml ');
Header (' Charset=utf-8 ');

Then echo out the XML.

