Handle remote data with PHP 5 and REST Web service

This Representational State Transfer (REST) Web service is made of three main parts: the login part, the xml part and the data part. The first part concerns about the validation of the user data: username, password, account id and IP address, which are all transferred and returned by the function file_get_contents(): It is supported by the function stream_context_create() which takes care of how the request will be made (for safety reasons POST). The second part (xml part) offers a HTTP-connection to an xml file with internal DTD on a remote server which is client side processed by SimpleXMLElement (from the PHP 5 SPL) for presentation and offers the complete CRUD handling (create, retrieve, update, delete) done by the DOM XML extension on the server side (if xml file is read- and writable!). The third part is simple database handling:with MySqli.