Add admin_menu_permission hook to menu.php

[donncha]

WordPress MU has a modified wp-admin/menu.php but with the addition of a new hook just above the user_can_access_admin_page() check, those custom mods can go into a new file.

I called the action admin_menu_permission as there are hooks above for modifying the admin menu, this hook wouldn't have any other function AFAICT.

I did try hooking on to admin_menu but it didn't work and the user received the standard WP "cannot access page" error instead of being redirected as WordPress MU usually does.

Please take a look at the attached file.

[westi]

Looking at the mu code (​http://trac.mu.wordpress.org/browser/trunk/wp-admin/menu.php) would we not do better with an action inside the failure case:

e.g.

if (! user_can_access_admin_page()) { 
    do_action('admin_page_access_denied');
    wp_die( __('You do not have sufficient permissions to access this page.') ); 
} 

mu can then hook on that and do the redirect if necessary before the wp_die

[westi]

This could also then be used by any WordPress plugins that wanted to track things like attempts to access pages that the user didn't have the rights to.

[donncha]

Good idea, looks better inside the if() condition.

[westi]

(In [6356]) Allow plugins to handle admin page access failures. Fixes #5379 props donncha