php get embed code from youtube url

1function convertYoutube($string) {
2    return preg_replace(
3        "/\s*[a-zA-Z\/\/:\.]*youtu(be.com\/watch\?v=|.be\/)([a-zA-Z0-9\-_]+)([a-zA-Z0-9\/\*\-\_\?\&\;\%\=\.]*)/i",
4        "<iframe src=\"//www.youtube.com/embed/$2\" allowfullscreen></iframe>",
5        $string
6    );
7}

1preg_replace("/\s*[a-zA-Z\/\/:\.]*youtube.com\/watch\?v=([a-zA-Z0-9\-_]+)([a-zA-Z0-9\/\*\-\_\?\&\;\%\=\.]*)/i","<iframe width=\"420\" height=\"315\" src=\"//www.youtube.com/embed/$1\" frameborder=\"0\" allowfullscreen></iframe>",$post_details['description']);