I'm trying to add a method to the Group class using a DataExtension. The module I am modifying already adds DataExtensions to the Member and Member_Validating classes like this:

  protected static function on_register() {
      Object::add_extension('Member', 'ExternalAuthenticatedRole');
      Object::add_extension('Member_Validator', 'ExternalAuthenticatedRole_Validator');
      return parent::on_register();
  }

So I added my own line, before line 2:

      Object::add_extension('Group', 'GroupObjectRole');

I added a file called GroupObjectRole.php to the same folder, and added a class GroupObjectRole extends DataExtension. However this results in a fatal error:

Fatal error: Object::add_extension() - Can't find extension class for "GroupObjectRole" in framework\core\Object.php on line 452

What am I doing wrong?

Did you try doing a ?flush=all, or even a /dev/build?flush=1?

Another error I've made is forget to add <?php to the top of the file, which I know is very stupid but gives the same resulting error :)

Done a /dev/build?flush=all and verified the <?php start but no luck.

Trying adding the

Object::add_extension('Group', 'GroupObjectRole');

to your _config.php in mysite(although this really shouldn't matter).

Double check the spelling of GroupObjectRole in your php file... A mistake i've often made.

And if you haven't try doing a ?flush=all without dev/build.