How to save the state of a drag and drop jQuery UI Sortables front end layout editor?

Brady is correct that the best way to handle saving and displaying of custom post type orders is by using the menu_order property

Here’s the jquery to make the list sortable and to pass the data via ajax to wordpress:

jQuery(document).ready(function($) {        
    var itemList = $('#sortable');

    itemList.sortable({
        update: function(event, ui) {
            $('#loading-animation').show(); // Show the animate loading gif while waiting

            opts = {
                url: ajaxurl, // ajaxurl is defined by WordPress and points to /wp-admin/admin-ajax.php
                type: 'POST',
                async: true,
                cache: false,
                dataType: 'json',
                data:{
                    action: 'item_sort', // Tell WordPress how to handle this ajax request
                    order: itemList.sortable('toArray').toString() // Passes ID's of list items in  1,3,2 format
                },
                success: function(response) {
                    $('#loading-animation').hide(); // Hide the loading animation
                    return; 
                },
                error: function(xhr,textStatus,e) {  // This can be expanded to provide more information
                    alert(e);
                    // alert('There was an error saving the updates');
                    $('#loading-animation').hide(); // Hide the loading animation
                    return; 
                }
            };
            $.ajax(opts);
        }
    }); 
});

Here’s the wordpress function that listens for the ajax callback and performs the changes on the DB:

function my_save_item_order() {
    global $wpdb;

    $order = explode(',', $_POST['order']);
    $counter = 0;
    foreach ($order as $item_id) {
        $wpdb->update($wpdb->posts, array( 'menu_order' => $counter ), array( 'ID' => $item_id) );
        $counter++;
    }
    die(1);
}
add_action('wp_ajax_item_sort', 'my_save_item_order');
add_action('wp_ajax_nopriv_item_sort', 'my_save_item_order');

The key to displaying the posts in the order you have saved is to add the menu_order property to the query args:

$args= array(
    'meta_key' => 'c3m_shown_on',
    'meta_value'=> 'home'
    'orderby' => 'menu_order',
    'order' => 'ASC'
);

$box_query = new WP_Query($args);

Then run your loop and output each item… (first line is the core wp loading animation – you’ll want to hide it initially via css, and then the jquery function will display when processing)

<img src="https://wordpress.stackexchange.com/questions/16342/<?php bloginfo("url'); ?>/wp-admin/images/loading.gif" id="loading-animation" />
<ul id="sortable">
    <li id="{echo post ID here}">{echo title or other name here}</li>
</ul>

Code inspired by soulsizzle’s excellent tutorial.