我使用php ajax获取每行数据的表

Question

嘿伙计们，所以我使用php ajax进行实时搜索，但我每行数据都会得到一个表格，我如何制作它以便所有行都在同一个表格中？这是home.php

    function showUser() {   
    var subject = document.getElementById("subject").value;
    var equipmentname = document.getElementById("equipmentname").value;
    if (subject == "" && equipmentname == "") {
        document.getElementById("txtHint").innerHTML = "";
        return;
    } else { 
        if (window.XMLHttpRequest) {
            // code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp = new XMLHttpRequest();
            // code for IE6, IE5
        } else {
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        xmlhttp.onreadystatechange = function() {
            if (this.readyState == 4 && this.status == 200) {
                document.getElementById("txtHint").innerHTML = this.responseText;
            }
        };
        xmlhttp.open("GET","getsubject.php?subject="+subject+"&equipmentname="+equipmentname,true);
        xmlhttp.send();
    }
}
</script>
<form style="margin-left:30%">
<select style="height:26px" name="subject" id="subject" onchange="showUser()">
  <option value="">Select Subject:</option>
  <option value="Physics">Physics</option>
  <option value="Chemistry">Chemistry</option>
  </select>
  <input type="text" name="equipmentname" id="equipmentname" onkeyup="showUser()">
</form>
<br>
<div id="txtHint">

这是getsubject.php`     

    <?php 
        $subject = strval($_GET['subject']);
        $itemname = strval ($_GET['itemname']);
include "connect.php";
$i="SELECT * FROM inventory WHERE ('$subject' = '' OR subject='".$subject."') AND ('$itemname' = '' OR equipmentname = '".$itemname."') ";
$h = mysql_query($i);
while($tr = mysql_fetch_array($h)) {

    ?>

<center>
    <table style="width:20%" class="table table-bordered table-striped">
            <tr>
                <td><?php echo $tr[0];?></td>
                <td><?php echo $tr[1];?></td>
                <td><?php echo $tr[2];?></td>               
            </tr>
    </table>
</center>
    <?php
            }
    ?>
</body>

`

感谢