The ARC2 documentation is not really precise. It gives the two following examples:
First, parsing an RDF file:
$parser = ARC2::getRDFParser();
$parser->parse('http://example.com/foaf.ttl');
$triples = $parser->getTriples();
Second, making a SPARQL query on a datastore:
$q = 'SELECT ...';
$rows = $store->query($q, 'rows');
…but would it be possible to make a SPARQL query over the parsed $triples
directly?