使用javascript更新数据库值

我有一个php应用程序，用于显示存储在数据库中的某些图片。我想使用JavaScript更改照片顺序。Index.php页面如下所示：

$photos = array();
$photos_query = "SELECT * FROM `photos` WHERE `id`=".$_SESSION['id']."ORDER BY `order`";
$data = mysqli_query($dbc, $photos_query);
while ($photos_row= mysqli_fetch_assoc($data)){
    $photos[] = array(
                'photo_id' => $photos_row['photo_id'], 
                'id' => $photos_row['id'], 
                'photo_name' => $photos_row['photo_name'], 
                'order' => $photos_row['photo_order']
            );
} ... 
<div id="message"></div>
<div id="showphotos">
    if (empty($photos)) {
        echo 'No photos';
    } else {
        echo '<ul>';
        foreach ($photos as $photo) {
            echo '<li id="photoid_'.$photo['photo_id'].'">
           <img src="uploads/', $photo['id'], '/', $photo['photo_id'],'"' .$photo['photo_name']. 'height="150" width="150">
           ...       </li>';    
        } echo '</ul>';
  }
</div>

用户尝试更改图像位置后，此页面将调用move.js：

$(document).ready(function(){   

    function slideOut(){
        setTimeout(function(){
            $("#message").slideUp("slow", function () {});
        }, 2000);
    };

    $("#message").hide();

    $(function() {
        $('ul').sortable({
            cursor: 'move',
            opacity: 0.7,
            revert: false,
            update: function(){
                var neworder = $(this).sortable("serialize") + '&update=update';
                $.post("change_image_position.php", neworder, function (themessage) {
                    $("#message").html(themessage);
                    $("#message").slideDown('slow');
                    slideOut();
                });
            }
        });
    });

});

最后，change_image_position.php包含：

$array = $_POST['photoid'];
if ($_POST['update'] == "update"){
    $count = 1;
    foreach ($array as $idval) {
        $query = "UPDATE photos SET order = " . $count . " WHERE photo_id = " . $idval;
        mysqli_query($query) or die('Error, insert query failed');
        $count ++;
    }
    echo 'All saved! refresh the page to see the changes';
} 

我面临两个问题...首先，按语句排序（index.php）不起作用，其次，通过数据库查询（change_image_position.php）查询更改照片的查询不返回任何结果。在此先感谢您的帮助。