function render($url = null)
{
if ($url === null) {
$prefixes = array_flip(Router::prefixes());
array_walk($prefixes, create_function('&$item', '$item = false;'));
$url = array('plugin' => 'kcaptcha', 'controller' => 'captcha', 'action' => 'render_captcha') + $prefixes;
}
return sprintf('<img src="%s" />', $this->url($url));
}