With PEAR's Tree you can process tree structures from different sources, be it a database result set or an XML document. An interesting characteristic of this package is that it allows you random access to tree nodes by using an element path, in a similar way as you would address a file in a filesystem. In the example in this slide we will use the file "%sdphp_talk.xml%". First we need to install it using the pear installer: Then we write a little bit of code to use our newly installed class.