// if url == http://localhost/photos/index.php/toto/titi, path_info == /toto/titi
// if url == http://localhost/photos/index.php, path_info is not set
// if url == http://localhost/photos/, path_info is not set
// if path_info is not set, we are at top level, so we redirect to /photos/index.php/
if (! isset($_SERVER["PATH_INFO"])) {
// if url == http://localhost/photos/index.php/toto/titi, path_info == /toto/titi
// if url == http://localhost/photos/index.php, path_info is not set
// if url == http://localhost/photos/, path_info is not set
// if path_info is not set, we are at top level, so we redirect to /photos/index.php/
if (! isset($_SERVER["PATH_INFO"])) {