I think the issue may be in your call to add_submenu_page()
:
add_submenu_page('wpsc-sales-logs',...
The first parameter needs to be a reference to your Menu Page’s “slug”, i.e. if you use 'edit.php'
instead you’ll see that you get a menu option under the “Posts” menu page:
add_submenu_page('edit.php','WPEC - Group Pricing','Group Pricing', 7,
'wp-e-commerce-group-pricing', 'price_options');
Here’s what it looks like:
(source: mikeschinkel.com)
So you need to find out what URL fragment (the part past http://yoursite.com/wp-admin/
) that your menu page uses.
UPDATE
For future readers, Roland’s issue was a hook priority issue. Changing priority from 10 to 11 fixed it in his case:
add_action('admin_menu', 'add_options_gp',11);
P.S. You really don’t need the if
statement testing for is_admin()
since you are using the 'admin_menu'
hook; it only fires in the admin.