มีปัญหาตอนดึงข้อมูลมาแก้ไข จังหวัด เขต แขวง ครับพี่ๆ

<script language=Javascript>
        function Inint_AJAX() {
           try { return new ActiveXObject("Msxml2.XMLHTTP");  } catch(e) {} //IE
           try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch(e) {} //IE
           try { return new XMLHttpRequest();          } catch(e) {} //Native Javascript
           alert("XMLHttpRequest not supported");
           return null;
        };

        function dochange(src, val) {
             var req = Inint_AJAX();
             req.onreadystatechange = function () { 
                  if (req.readyState==4) {
                       if (req.status==200) {
                            document.getElementById(src).innerHTML=req.responseText; //รับค่ากลับมา
                       } 
                  }
             };
             req.open("GET", "localtion.php?data="+src+"&val="+val); //สร้าง connection
             req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=utf-8"); // set Header
             req.send(null); //ส่งค่า
        }

        window.onLoad=dochange('province', -1);     
</script>


<tr>
				<td><label>จังหวัด</label><span id="red">**</span></td>
				<td>
                <span id="province">
                	<div class="col-lg-5">
                    <select class="form-control text_select_post" name="province">
                        <option value="">-- เลือกจังหวัด --</option>
                    </select>
                    </div>
                </span>
                </td>
            </tr>
            <tr>
            	<td><label>อำเภอ / เขต</label><span id="red">**</span></td>
				<td>    
                <span id="amphur">
                	<div class="col-lg-5">
                    <select class="form-control text_select_post" name="amphur">
                        <option value=''>-- เลือก อำเภอ / เขต --</option>
                    </select>
                    </div>
                </span>
                </td>
           	</tr>
           	<tr>
           		<td><label>ตำบล / แขวง</label><span id="red">**</span></td>
				<td>
                <span id="district">
                	<div class="col-lg-5">
                    <select class="form-control text_select_post" name="district">
                        <option value=''>-- เลือก ตำบล / แขวง --</option>
                    </select>
                    </div>
                </span>
                </td>
			</tr>

include "config.php";
    conndb();

    echo $data = $_GET['data'];
    echo $val = $_GET['val'];


         if ($data=='province') { 
              echo "<select class='text_select_post' name='province' onChange=\"dochange('amphur', this.value)\">";
              echo "<option value='0'>-- เลือกจังหวัด --</option>\n";
              $result=mysql_query("select * from province order by PROVINCE_NAME");
              while($row = mysql_fetch_array($result)){
                   echo "<option value='$row[PROVINCE_ID]'>$row[PROVINCE_NAME]</option>" ;
              }
         } else if ($data=='amphur') {
              echo "<select class='text_select_post' name='amphur' onChange=\"dochange('district', this.value)\">";
              echo "<option value='0'>-- เลือก อำเภอ / เขต --</option>\n";                             
              $result=mysql_query("SELECT * FROM amphur WHERE PROVINCE_ID= '$val' ORDER BY AMPHUR_NAME");
              while($row = mysql_fetch_array($result)){
                   echo "<option value=\"$row[AMPHUR_ID]\">$row[AMPHUR_NAME]</option>";
              }
         } else if ($data=='district') {
              echo "<select class='text_select_post' name='district'>\n";
              echo "<option value='0'>-- เลือก ตำบล / แขวง --</option>\n";
              $result=mysql_query("SELECT * FROM district WHERE AMPHUR_ID= '$val' ORDER BY DISTRICT_NAME");
              while($row = mysql_fetch_array($result)){
                   echo "<option value=\"$row[DISTRICT_ID]\">$row[DISTRICT_NAME]</option>\n";
              }
         }
         echo "</select>\n";

        echo mysql_error();
        closedb();