If the namespace is nested in the xml, then you will have to loop over the nodes.
<?php
$xml = <<<XML
<?xml version="1.0" encoding="UTF-8"?>
  <people xmlns:p="http://example.org/ns" xmlns:t="http://example.org/test">
      <items>
            <title>This is a test of namespaces and my patience</title>
            <p:person id="1">John Doe</p:person>
            <p:person id="2">Susie Q. Public</p:person>
            <p:person id="1">Fish Man</p:person>
      </items>
  </people>
XML;
$sxe = new SimpleXMLElement($xml);
foreach ($sxe as $out_ns)
{
    $ns = $out_ns->getNamespaces(true);
    $child = $out_ns->children($ns['p']);
    foreach ($child as $out)
    {
        echo $out . "<br />";
    }
}
?>