$url = 'https://www.youtube.com/watch?v=j5-yKhDd64s';
    $data = exec("youtube-dl -j ".$url);
    var_dump($data);

720 1 = https://r1---sn-a5msen7l.googlevideo.com/videoplayback?ei=***********
480 1 = https://r1---sn-a5msen7l.googlevideo.com/videoplayback?ei=***********
360 1 = https://r1---sn-a5msen7l.googlevideo.com/videoplayback?ei=***********
m4a 1 = https://r1---sn-a5msen7l.googlevideo.com/videoplayback?ei=***********