使用 AJAX 发布 PHP 数组值

我试图使用 ajax 发送一个 php 数组值，但什么也没发生，MySQL 表也没有更新......

.html：

//edit topic
if(isset($_GET['edit_topic']) && is_numeric($_GET['edit_topic'])  ){
    $topic_id=htmlspecialchars($_GET['edit_topic']);

$get_topic=$db->query("select * from articles where art_id='$topic_id'");
    $topic=$get_topic->fetch_assoc();
    ?>
    <form role="form"  action="" id="edit_topic_form" method="post">
    <div class="row">
    <div class="col-md-6">عنوان الموضوع</div>
    <div class="col-md-6"><input type="text" class="form-control" name="art_title" id="art_title" value="<?php echo $topic['art_title']; ?>"></div>
    </div>
.........................
    </form>
    <?php

}

.php：

if($_POST){
        $topic_array=array(
        "art_title"=>$_POST['art_title'],
        "art_subtitle"=>$_POST['art_subtitle'],
        "art_desc"=>$_POST['art_desc'],
        "art_tags"=>$_POST['art_tags'],
        "art_download"=>$_POST['art_download'],
        "art_yt"=>$_POST['art_yt'],
        "art_instructor"=>$_POST['art_instructor'],
        "art_com_no"=>$_POST['art_com_no'],
        "art_likes"=>$_POST['art_likes']
        );
        $update_topic=$db->query("update articles set 
        art_title='".$topic_array['art_title']."',
        art_subtitle='".$topic_array['art_subtitle']."',
        art_desc='".$topic_array['art_desc']."',
        art_tags='".$topic_array['art_tags']."',
        art_download='".$topic_array['art_download']."',
        art_yt='".$topic_array['art_yt']."',
        art_instructor='".$topic_array['art_instructor']."',
        art_com_no='".$topic_array['art_com_no']."',
        art_likes='".$topic_array['art_likes']."'
        where art_id='$topic_id'
        ");
        }

jquery：

$(document).ready(function(){
var request;
$("#edit_topic_form").submit(function(event){

    if (request) {
        request.abort();
    }
    var $form = $(this);
    var $inputs = $form.find("input, select, button, textarea");
    var serializedData = $form.serialize();
    $inputs.prop("disabled", true);

    request = $.ajax({
        url: "dashboard.php",
        type: "post",
        data: serializedData
    });

    request.done(function (response, textStatus, jqXHR){
        // Log a message to the console
       alert("تم تعديل الموضوع بنجاح");
    });

    request.always(function () {
        // Reenable the inputs
        $inputs.prop("disabled", false);
    });

    event.preventDefault();
});


    })