$btc = new \Shucream0117\Bitcoin\Bitcoin(
    'username', // rpcuser
    'password', // rpcpassword
    'localhost', // host
    19402, // port
    false // if use HTTPS
);

$response = $btc->callApi('getinfo');
$responseArray = json_decode($response->getBody()->getContents(), true);
var_dump($responseArray);

// arguments can be passed as array
// array[0] is argument1, array[1] is argument2...
$response = $btc->callApi(
    'gettransaction',
    ['dee2406ae3ed5e1edc923d69ba795edfc9e01e5cc632ed8b7bb4365df5b106c9']
);