auto-populate wpmenu with pages and child pages (code runs on update/save/delete pages)

snippet.php

<?php

function x_auto_populate_menu() {
	
    $menu_id = 123; // Replace with your actual menu ID

    if (!$menu_id) {
        return; // Exit if no menu ID is set
    }

    // Get all pages
    $pages = get_pages(['sort_column' => 'menu_order']);

    // Get current menu items
    $menu_items = wp_get_nav_menu_items($menu_id);
    $existing_items = [];

    if ($menu_items) {
        foreach ($menu_items as $item) {
            $existing_items[$item->object_id] = $item->ID;
        }
    }

    // Clear existing menu items
    if (!empty($existing_items)) {
        foreach ($existing_items as $item_id) {
            wp_delete_post($item_id, true);
        }
    }

    // Build a list of menu item IDs for parent-child relationships
    $menu_item_ids = [];

    // Add pages to the menu
    foreach ($pages as $page) {
        $parent_id = 0;

        // Check if the page has a parent
        if ($page->post_parent && isset($menu_item_ids[$page->post_parent])) {
            $parent_id = $menu_item_ids[$page->post_parent];
        }

        // Add the page as a menu item
        $menu_item_id = wp_update_nav_menu_item($menu_id, 0, [
            'menu-item-title'     => $page->post_title,
            'menu-item-object'    => 'page',
            'menu-item-object-id' => $page->ID,
            'menu-item-type'      => 'post_type',
            'menu-item-status'    => 'publish',
            'menu-item-parent-id' => $parent_id,
        ]);

        // Store menu item ID for parent-child mapping
        $menu_item_ids[$page->ID] = $menu_item_id;
    }
}

// Hook into post save and delete to refresh menu when pages change
function x_trigger_menu_update($post_id) {
    // Run only for published pages
    if (get_post_type($post_id) === 'page') {
        x_auto_populate_menu();
    }
}

// Run when a page is added, updated, or deleted
add_action('save_post', 'x_trigger_menu_update');
add_action('delete_post', 'x_trigger_menu_update');