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

I am building a front end post layout editor using jQuery UI Sortable.

The posts are laid out in 300px by 250px boxes over a background image. The posts are created and edited using the WordPress admin but I want to allow the sites administrator to adjust the order of the boxes using a drag and drop interface on the front end.

I’ve got the drag and drop sortable part working but need to come up with a way to save the state (order) of the boxes. Ideally I would like to be able to save the state as an option and build it into the query.

The query for the posts is a simple WP_Query that also gets data from custom meta boxes to determine the individual box layout.:

$args= array(
      'meta_key' => 'c3m_shown_on',
       'meta_value'=> 'home' );
    $box_query = new WP_Query($args);  ?>
        <ul id="sortable">
            <?php
    while ($box_query->have_posts()) : $box_query->the_post(); global $post; global $prefix;           
    $box_size = c3m_get_field($prefix.'box_size', FALSE);
    $box_image = c3m_get_field($prefix.'post_box_image', FALSE);
    $overlay_class = c3m_get_field($prefix.'overlay_class', FALSE);
    
    if ( c3m_get_field($prefix.'external_link', FALSE) ) {
    $post_link = c3m_get_field($prefix.'external_link', FALSE);
    } else
            { $post_link = post_permalink(); 
    } ?>     
     <li class="<?php echo $box_size;?>  ui-state-default">
        <article <?php post_class() ?> id="post-<?php the_ID(); ?>">
            <?php echo  '<a href="'.$post_link.'" ><img src="'.esc_url($box_image).'" alt="Image via xxxxx.com" /></a>'; ?>
                <div class="post-box <?php echo $overlay_class;?>">
                <?php if ( c3m_get_field( $prefix.'text_display', FALSE) ) { ?>     
                <h2><a href="<?php echo $post_link?>"><?php the_title();?></a></h2> 
                <p><?php echo substr($post->post_excerpt, 0, 90) . '...'; ?></p>            
                <?php } ?>               
                </div>
         </article>
     </li>              
    <?php endwhile; ?>
       </ul>
</section>

The javascript is just the basic default sortable instructions

jQuery(document).ready(function() {
    jQuery("#sortable").sortable();
  });

There are methods available using cookies to save the state but I also need to disable the sortable drag and drop for non admin users so I really need to save to the database.

I’m looking for the most creative and usable method and will award a 100 point bounty to the best answer.

Update:

I got somatic’s answer working with one minor change.

ajaxurl doesn’t return the value on non admin pages so I used wp_localize_script( 'functions', 'MyAjax', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) ); to define the value and changed the javascript line under options to:
url: MyAjax.ajaxurl,

To limit access to arranging the order to only admins I added a conditional to my wp_enqueue_script function:

    function c3m_load_scripts() { 
    if ( current_user_can( 'edit_posts' ) ) {
        wp_enqueue_script( 'jquery-ui' );
        wp_enqueue_script( 'functions', get_bloginfo( 'stylesheet_directory' ) . '/_/js/functions.js', array( 'jquery', 'jquery-ui' ), false);
        wp_localize_script( 'functions', 'MyAjax', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) );
    }
}

I’m going to do a little more testing and mark this question as solved and award the bounty.

3

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.

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