public function getDuration($full_video_path)
{
    $getID3 = new \getID3;
    $file = $getID3->analyze($full_video_path);
    $playtime_seconds = $file['playtime_seconds'];
    $duration = date('H:i:s.v', $playtime_seconds);

    return $duration;
}

This is a very slow process. When you upload a video, it will take more time than a regular upload.