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CHAPTER 20 • WEB SERVICESwww.it-ebooks.infoJake BarnesLady Brett AshleyRobert CohnMike CampbellUsing XPath to Retrieve Node InformationXPath is a W3C standard that offers an intuitive, path-based syntax for identifying XML nodes.SimpleXML offers a method called xpath() for doing so, and its prototype follows:array simplexml_element->xpath(string path)XPath also offers a set of functions for selectively retrieving nodes based on value. For example,referring to the books.xml document, you could use the xpath() method to retrieve all author nodesusing the expression /library/book/author:xpath("/library/book/author");foreach($authors AS $author) {echo "$author";}?>This example returns the following:Jane AustenAlberto MoraviaErnest HemingwayYou can also use XPath functions to selectively retrieve a node and its children based on a particularvalue. For example, suppose you want to retrieve all book titles where the author is named “ErnestHemingway”:xpath("/library/book[author='Ernest Hemingway']");echo $book[0]->title;?>This example returns the following:The Sun Also Rises424