This was the answer to a question that came in an email - "Do you know of a good XML to JSON converter?"
Obviously you need php-cli, JSON, and SimpleXML. :)
The "xml" is the name of the file that contains the XML, the output can be piped to a different file.
php -r 'echo json_encode(simplexml_load_file("xml"));'
If you would like it pretty printed, this page is really nice: http://jsonprettyprint.com/