Web Services are typically application programming interfaces (APIs) or web APIs that are accessed via Hypertext Transfer Protocol (HTTP) and executed on a remote system hosting the requested services.
RSS offers a formalized means for encapsulating a web site’s content within an XML-based structure, known as a feed. It is based on the premise that most site information shares a similar format, regardless of topic.
For example, although sports, weather, and theater are dissimilar topics, the news items published under each share a similar structure: a title, an author, a publication date, a URL, and a description.
A number of SimpleXML functions are available for loading and parsing the XML document.
Loading XML from File
The simplexml_load_file() function loads an XML file into an object.
$xml = simplexml_load_file("books.xml");
If a problem is encountered loading the file, FALSE is returned.
Loading XML from a String
If the XML document is stored in a variable, you can use the simplexml_load_string() function to read it into the object. This function is identical in purpose to simplexml_load_file(), except that the input parameter is expected in the form of a string rather than a file name.
Learning More About an Element
XML attributes provide additional information about an XML element. You can use the attributes() method to retrieve these attributes. For example,
Learning About a Node's Children
You can use the children() method if you are interested only in a particular node's children.
Using XPath to Retrieve Node Information
XPath is a W3C standard that offers path-based syntax for identifying XML nodes. SimpleXML offers a method called xpath() for doing so. For example,
$authors = $xml->xpath("/library/book/author");
XPath also offers a set of functions for selectively retrieving nodes based on value. For example,
$book = $xml->xpath("/library/book[author='Ernest Hemingway']");