tinymce, find youtube url, replace it with embed iframe

$str = '<iframe src="https://www.youtube.com/embed/bqjK_Gd0mhc" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>';
$pattern = '/<iframe.*?src="(.*?)".*?<\/iframe>/';
preg_match($pattern, $str, $matches);
if ($matches) {
    $embed_url = str_replace("watch?v=", "embed/", $matches[1]);
    echo '<iframe width="560" height="315" src="'.$embed_url.'" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>';
}