This is what you want to read. It will tell ya what ya want to know
PhotoPost Enhanced vB3 Index Integration
As I stated the new files are inc_features.php and inc_photopost.php files are all new. You got an error trying to use inc_features.php because you still had an old inc_photopost.php file included also instead of uploading the new one which does not have the pp_get_ext in it anymore.