How to set default metaboxes on user creation?

Question

Just for repetition's sake, I want to do the following: I need to set custom fields and the excerpt metaboxes for WP default Posts post type when a new user is created. I know that by default WP doesn't show them but would like it to. I will be removing the Screen Options tab so the user won't be able to disable them.

I know this question has been asked for different scenarios and I have tried using and changing the code that I found here and on the web that help manipulate this but without much luck (eg: How to set default screen options?). Obviously I've tried on different installs but it doesn't work. Is there another way of doing this?

Answer 1

Based on this Answer by t31os.

Here, all meta boxes are being set to invisible, so simply remove from the array the ones that are meant to be visible.

add_action('user_register', 'wpse_58645_set_user_metaboxes');

function wpse_58645_set_user_metaboxes( $user_id ) 
{
    update_user_meta( 
        $user_id, 
        'metaboxhidden_post', 
        array( 
            'authordiv',
            'categorydiv',
            'commentstatusdiv',
            'formatdiv',
            'postcustom',
            'postexcerpt',
            'postimagediv',
            'slugdiv',
            'tagsdiv-post_tag',
            'trackbacksdiv',
        ) 
    );
}

For registered users, running an admin_init only once will do, but this is just the concept:

$blogusers = get_users('blog_id=1');

foreach ( $blogusers as $user ) 
{
    if ( !get_user_meta( $user->ID, 'metaboxhidden_post', true ) ) 
    {
        update_user_meta( $user->ID, 'metaboxhidden_post', $meta_value );
    }
}