PDO->bindParam, PDO->bindValue and PDO->closeCursor


So far I have been using PDO->bindParam however while reading the manual I found PDO->bindValue from what I can tell PDO->bindValue passes by value where as PDO->bindParam passes by reference, is this the only difference?

$modThread = db()->prepare("UPDATE `threads` SET `modtime` = UNIX_TIMESTAMP( ) WHERE `threadid` =:id LIMIT 1");

        $modThread->bindParam(':id', $thread);

Again while reading the manual I found: PDO->closeCursor should I place it where marked? Is it optional/automatically called? Seems only certain drivers need it. Will calling it on a driver that doesn't need/support it cause errors? How about MySQL?