Curl allows you to connect and communicate to remote servers. XML Travel Client uses Curl to talk to WCT's servers and return the xml data.

Smarty is a template engine for PHP. More specifically, it facilitates a managable way to separate application logic and content from its presentation.

XML (eXtensible Markup Language) is a data format for structured document interchange on the Web. It is a standard defined by The World Wide Web consortium (W3C). Information about XML and related technologies can be found at http://www.w3.org/XML/.