XML and PHP

Hi! I've been looking at the XML-parserfunctions in the manual, and they seems nice enough. But I'm currently in a project where there is need to read from, write to and edit in XML-files, in some smart way. Our ISP is supporting the following: xml XML Support active XML Namespace Support active EXPAT Version 1.95.6 I suppose the answer to my questions lies in the expath-part, but where do I start, where can I read more about the above expat and which is the best approach for me in this project? We're going to import som data from Navision, XML-formatted, to postgresql, and meanwhile documents are edited they are, until finished, going to be saved as xml-documents on the server. Sincerely Victor