how to get the "content" with "xmlDoc" or "xmlDocFile"?

I have some problem in using domxml in php
how to get the "content" with "xmlDoc" or "xmlDocFile"?
I use Php 4.2.0 , and try this script :

<?php
$theXML = "<?xml version='1.0'?>";
$theXML .= " <people>";
$theXML .= " <person id='13' dob='13/07/82'>";
$theXML .= " Mitchell Harper";
$theXML .= " </person>";
$theXML .= " <person id='14' dob='20/08/1960'>";
$theXML .= " Bodger Dodger";
$theXML .= " </person>";
$theXML .= " </people>";
$xmlDoc = xmldoc($theXML);
$root = $xmlDoc->root();
$people = $root->children();
while($person = array_shift($people))
{
if($person->tagname == "person")
{
echo "<b>Person Found:</b><br> ";
echo "Name: " . $person->content . "<br>";
echo "Id: " . $person->get_attribute("id") . "<br>";
echo "DOB: " . $person->get_attribute("dob") . "<br><br>";
}
}
?>

and why the
$person->content
still does'nt appear, what's wrong with this?
but if i use
$xmlDoc = xmltree($theXML);
and
$person->chidren[0]->content
I get the content