$summary = $element->query('itunes:summary');
$summary = $element->query('{http://www.itunes.com/dtds/podcast-1.0.dtd}summary');
$summary = $element->query('summary')
$summary = $element->query(process_name('itunes:summary'):
$summary = $element->query(process_name('{http://www.itunes.com/dtds/podcast-1.0.dtd}summary'):