Access to attribute in SimpleXML

gistfile1.php

<?php

header('Content-Type: text/html; charset=utf-8');

$s = file_get_contents('http://bananadream-monkey:8983/solr/select/?q=%D0%BF%D1%83%D1%88%D0%BA%D0%B8%D0%BD%0D%0A&version=2.2&start=0&rows=10&indent=on');
$xml = simplexml_load_string($s);

$doc = $xml->result->doc[0];

echo $doc->str[0]->attributes()->name;