Change the post thumbnail URL

// NAV: Change the url for thumbnail for post
function wpcoder_change_post_thumbnail_url($url, $post_id) {
if (strpos($url, 'img/uploads/') !== false) {
$year = date('Y'); // Year folder
$month = date('m'); // Month folder
$url =  str_replace("img/uploads/", "app/uploads/", $url);
}
return $url;
}
add_filter('wp_get_attachment_url', 'wpcoder_change_post_thumbnail_url', 10, 2);