How can I get ALL the capabilities of an existing user role (eg. Author) ? I'll be using it to quickly duplicate an existing user role, then create a new role then assign or remove capabilities to a new custom role.
I suggest not to mess with the existing roles and capabilities in its default, it might help you some trouble when you will have a bunch of custom roles and capabilities in the future.
To answer your question, I will have an example: I need new role/user group that has almost an Administrator but don't have the the capability to edit plugins and the theme, to do that:
1) Let's say you would like to copy the existing capabilities of Administrator, do it by:
$admin_role_set = get_role( 'administrator' )->capabilities;
2) You can create a new user role by using add_role, see Codex for more details. We can then use the list of capabilities that we have from #1 by using:
$role = 'content_admin'; $display_name = 'Content Admin'; add_role( $role, $display_name, $admin_role_set );
3) By checking the Roles and Capabilities list from the codex: https://codex.wordpress.org/Roles_and_Capabilities we will be needing to remove edit_plugins & edit_themes capabilities, we can achieve that by using remove_cap():
remove_cap( 'editor', 'edit_plugins' ); remove_cap( 'editor', 'edit_themes' );
Hope this helps!