Custom Category Sort

<?php
add_action('category_add_form_fields', 'category_metabox_add', 10, 1);
add_action('category_edit_form_fields', 'category_metabox_edit', 10, 1);
add_action('created_category', 'save_category_meta_data', 10, 1);
add_action('edited_category', 'save_category_meta_data', 10, 1);

function category_metabox_add($tag)
{
?>
    <div class="form-field">
        <label for="tax-order"><?php _e('Order') ?></label>
        <input name="tax-order" id="tax-order" type="text" value="" size="40" aria-required="true" />
        <p class="description"><?php _e('Determines the order in which the term is displayed.'); ?></p>
    </div>
<?php
}

function category_metabox_edit($tag)
{
?>
    <tr class="form-field">
        <th scope="row" valign="top">
            <label for="tax-order"><?php _e('Order'); ?></label>
        </th>
        <td>
            <input name="tax-order" id="tax-order" type="text" value="<?php echo get_term_meta($tag->term_id, 'tax-order', true); ?>" size="40" aria-required="true" />
            <p class="description"><?php _e('Determines the order in which the term is displayed.'); ?></p>
        </td>
    </tr>
<?php
}

function save_category_meta_data($term_id)
{
    if (isset($_POST['tax-order']))
        update_term_meta( $term_id, 'tax-order', $_POST['tax-order']);
}

add_filter('get_terms', 'custom_term_sort', 10, 3);

function custom_term_sort($terms, $taxonomies, $args)
{
    // Controls behavior when get_terms is called at unusual times resulting in a terms array without objects
    $empty = false;

    // Create collector arrays
    $ordered_terms = array();
    $unordered_terms = array();

    // Add taxonomy order to terms
    foreach($terms as $term)
    {
        // Only set tax_order if value is an object
        if(is_object($term))
        {
            if($taxonomy_sort = get_term_meta($term->term_id, 'tax-order', true))
            {
                $term->tax_order = (int) $taxonomy_sort;
                $ordered_terms[] = $term;
            }
            else
            {
                $term->tax_order = (int) 0;
                $unordered_terms[] = $term;
            }
        }
        else
            $empty = true;
    }

    // Only sort by tax_order if there are items to sort, otherwise return the original array
    if(!$empty && count($ordered_terms) > 0)
        quickSort($ordered_terms);
    else
        return $terms;

    // Combine the newly ordered items with the unordered items and return
    return array_merge($ordered_terms, $unordered_terms);
}

function quickSort(&$array)
{
    $cur = 1;
    $stack[1]['l'] = 0;
    $stack[1]['r'] = count($array)-1;

    do
    {
        $l = $stack[$cur]['l'];
        $r = $stack[$cur]['r'];
        $cur--;

        do
        {
            $i = $l;
            $j = $r;
            $tmp = $array[(int)( ($l+$r)/2 )];

            // partion the array in two parts.
            // left from $tmp are with smaller values,
            // right from $tmp are with bigger ones
            do
            {
                while( $array[$i]->tax_order < $tmp->tax_order )
                $i++;

                while( $tmp->tax_order < $array[$j]->tax_order )
                $j--;

                // swap elements from the two sides
                if( $i <= $j)
                {
                     $w = $array[$i];
                     $array[$i] = $array[$j];
                     $array[$j] = $w;

                    $i++;
                    $j--;
                }

            }while( $i <= $j );

            if( $i < $r )
            {
                $cur++;
                $stack[$cur]['l'] = $i;
                $stack[$cur]['r'] = $r;
            }
            $r = $j;

        }while( $l < $r );

    }while( $cur != 0 );
}
?>