实时编辑文本ajax php

我有文本区，并使用ajax插入数据到数据库，但我希望能够编辑文本区现场，就像facebook一样，当你编辑评论。到目前为止，我已经得到的数据插入到数据库，但我不能得到文本区消失，并显示插入的文本。有人能给我点提示吗?

<textarea row="5" col="20" id="md">
<button href="javascript:void(0);" onclick="mdmsg();">Save</button>

js

function mdmsg() {
    var md = $("#md").val();
    if (md == "") {
        $("#errormsg").fadeIn('slow').html('<div class="errorreg">enter some text.</div>');
    } else {
        var dataString = 'md=' + md;
        $.ajax({
            type: "POST",
            url: "test?targ=mdmsg",
            data: dataString,
            success: function (response) {
                $('#md').html(response);
            }
        });
    }
}

if(isset($_GET["targ"]) == "mdmsg")             
{ 
    $cont = $_POST['md'];
    $upd = $db->prepare("update users set bio = ? where user_name  = ?");
    echo $db->error;
    $upd->bind_param('ss', $cont, $username->username);
    $upd->execute();
    echo "success";
    $hg = $db->prepare("select `bio` from users where user_name = ?");
    echo $db->error;
    $hg->bind_param('s', $username->username);
    $hg->execute();
    $res = $hg->get_result();
    while($row = $res->fetch_assoc())
    {
        echo "<div id='dvv'>".$row['bio']."</div>";//I want this row to show up on the textarea.
    }
}