PHP遍历XML文档所有节点的方法

<contact id="43956">   <personal>     <name>        <first>J</first>        <middle>J</middle>        <last>J</last>     </name>     <title>Manager</title>     <employer>National</employer>     <dob>1971-12-22</dob>   </personal></contact>

<?php   function walk_tree ($node, $depth = 0) {     for ($i = 0, $indent = ''; $i < $depth; $i++)        $indent .= '   ';     if ($node->type == XML_ELEMENT_NODE) {        print ($indent . $node->tagname . "/n");        $kids = $node->children ();        $nkids = count ($kids);        if ($nkids > 0) {           $depth++;           for ($i = 0; $i < $nkids; $i++)             walk_tree ($kids[$i], $depth);           $depth--;        }     }   }   $doc = xmldocfile ('contact.xml');   print ("<pre>/n");   walk_tree ($doc->root ());   print ("</pre>/n");?>