Reorder custom submenu item

Question

In the Settings menu, I have the following menu items listed:

Settings
-- General
-- Writing
-- Reading
-- Discussion
-- Media
-- Permalinks
-- Blogging

I'd like to the Blogging (options-general.php?page=blogging) reordered underneath General instead of being at the bottom. This was added with the add_options_page() function.

From doing some research, this is what I've come up with:

add_filter( 'custom_menu_order', array( $this, 'submenu_order' ) );
function submenu_order( $menu_order ) {
    global $submenu;
    $order = array();
    $order[] = $submenu['options-general.php'][10];
    $order[] = $submenu['options-general.php'][41];
    $submenu['options-general.php'] = $order;
    return $menu_order;
}

This works, but it only shows General and Blogging, the rest are removed:

Settings
-- General
-- Blogging

Also, $submenu['options-general.php'][41] is currently index position 41 for me. Does this mean it will be the same index position for everyone else even if they have another plugin settings listed?

Answer 1

Got it, thanks to cjbj's help, I was able to get the final solution:

add_filter( 'custom_menu_order', 'submenu_order' );
function submenu_order( $menu_order ) {
    # Get submenu key location based on slug
    global $submenu;
    $settings = $submenu['options-general.php'];
    foreach ( $settings as $key => $details ) {
        if ( $details[2] == 'blogging' ) {
            $index = $key;
        }
    }
    # Set the 'Blogging' menu below 'General'
    $submenu['options-general.php'][11] = $submenu['options-general.php'][$index];
    unset( $submenu['options-general.php'][$index] );
    # Reorder the menu based on the keys in ascending order
    ksort( $submenu['options-general.php'] );
    # Return the new submenu order
    return $menu_order;
}

Answer 2

The result you get is not surprising, given that you're directly manipulating a global variable. You're replacing $submenu with only the items with keys 10 and 41. If you want to follow this method you would need to do this (assuming there's nothing at key 11):

$submenu['options-general.php'][11] = $submenu['options-general.php'][41];
unset ($submenu['options-general.php'][41]);

However, note that you are not using the filter function in any way. Nothing happens to the $menu_order that you are passing through the filter. So, this cannot be a very clean solution.

As you doubtlessly have seen, add_submenu_page simply adds a new submenu at the end of the array in the order the function is called. This line:

$submenu[$parent_slug][] = array ( $menu_title, $capability, $menu_slug, $page_title );

So if a new plugin would call add_submenu_page before you do, the key of 41 could easily be a different one. To prevent this you would have to loop through $submenu to find the correct key. Quick 'n dirty version:

for ( $i = 1; $i <= 100; $i++ ) {
    if ( array_key_exists( $submenu['options-general.php'][$i] ) ) {
        if ( $submenu['options-general.php'][$i][2] == 'my-custom-slug' ) {
            $the_desired_key = $i;
            // [2] because that is the index of the slug in the submenu item array above
        }
    }
}

UPDATE

Better version of the latter loop:

$sub = $submenu['options-general.php'];
foreach ( $sub as $key => $details ) {
        if ( $details[2] == 'my-custom-slug' ) {
            $the_desired_key = $key;
        }
  }

After finding $the_desired_key in this way, you can safely use the set+unset method above. I've verified 11 is an unused offset.