Is it possible to extract RDFa from html page using EasyRdf?

Question

I'm trying to extract RDFa data from an html page using EasyRDF. But it doesn't seem to work. E.g., I've tried:

$work = new EasyRdf_Graph("http://example.com/");
$work->load();
echo $work;
$title = $work->primaryTopic();
echo "Title: ".$title->get('dc:title')."\n";

This is the error I get:

Fatal error: Uncaught exception 'InvalidArgumentException' with message 'EasyRdf_Http_Client only supports the 'http' and 'https' schemes.'