tinymce, find youtube url, replace it with embed iframe

function replace_youtube($text) {
    $regex = '@(http(s)?)?(://)?(([a-zA-Z])([-\w]+\.)+([^\s\.]+[^\s]*)+[^,.\s])@';
    $url = $text;
    $result = preg_replace($regex, "<iframe width='560' height='315' src='http://www.youtube.com/embed/$0' frameborder='0' allowfullscreen></iframe>", $url);
    return $result;
}