use Solarium\Client;
use Solarium\QueryType\System\Query as SystemQuery;

$client->registerQueryType(SystemQuery::QUERY_SYSTEM, 'Solarium\\QueryType\\System\\Query');
$system = $client->createQuery(SystemQuery::QUERY_SYSTEM);
$result = $client->execute($system);

print 'Schema: ' . $result->getCoreSchema(); . PHP_EOL;