preg_match('@type="text/javascript" src="(http://api\.recaptcha\.net/challenge\?k=[^"]*)">@', $page, $matches);
    $rcjs = $matches[1];

    $page = get($rcjs);

    preg_match("@challenge : '([^']*)'@", $page, $matches);
    $challenge = $matches[1];

    $url = "http://api.recaptcha.net/image?c=$challenge";