(PHP 4 >= 4.1.0)
DomNode::next_sibling — Returns the next sibling of node
   This function returns the next sibling of the current node. If there is
   no next sibling it returns FALSE (< 4.3) or null (>= 4.3). You can 
   use this function to iterate over all children of a node as shown in the 
   example.
  
Example #1 Iterate over children
<?php
include("example.inc");
if (!$dom = domxml_open_mem($xmlstr)) {
  echo "Error while parsing the document\n";
  exit;
}
$elements = $dom->get_elements_by_tagname("tbody");
$element = $elements[0];
$child = $element->first_child();
while ($child) {
   print_r($child);
   $child = $child->next_sibling();
}
?>
See also domnode_previous_sibling().