Usually, people use children().
$rss = simplexml_load_string(
'<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0" xmlns:moshtix="http://www.moshtix.com.au">
<channel>
<link>qweqwe</link>
<moshtix:genre>asdasd</moshtix:genre>
</channel>
</rss>'
);
foreach ($rss->channel as $channel)
{
echo 'link: ', $channel->link, "\n";
echo 'genre: ', $channel->children('moshtix', true)->genre, "\n";
}