in object oriented php mysqli

I am trying to request a username, and return if it matches a row, without actually returning any user data.

How would I write this?...so far I have...

$sql = "SELECT NULL FROM database WHERE usernick=?";
$stmt = $link->prepare($sql)
$stmt->bind_param('s', $snr);
$stmt->execute();

After this step I need to see if a row matched the query...but I have no idea how to write it, everyone here pretty much writes in mysql if I dont mention I want object oriented mysqli :S