Динамическая таблица

datebase name: destination
id:1
company_name: kebstor
code_phone: 79
billing_destination:Russia-Beeline
price: 0.7

index.php

<script>
function showUser(str) {
    if (str == "") {
        document.getElementById("txtHint").innerHTML = "";
        return;
    } else {
        if (window.XMLHttpRequest) {
            // code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp = new XMLHttpRequest();
        } else {
            // code for IE6, IE5
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        xmlhttp.onreadystatechange = function() {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                document.getElementById("txtHint").innerHTML = xmlhttp.responseText;
            }
        }
        xmlhttp.open("GET","destination_get.php?q="+str,true);
        xmlhttp.send();
    }
}
</script>
<div id="content">
<div id="mainContent">
<h3><span class='name'>Interconect</span></h3>  
<p>&nbsp;</p>
<td><b>Customers:</b></td>
<Td>
<?php $query=mysqli_query($link,"Select id FROM destination"); ?>
<select name="billing_destination" class="form"  onchange="showUser(this.value)">
<option value="">Select Destination:</option>
<?php while($data=mysqli_fetch_array($query)){ ?>
<option value="<?php echo $data['id'] ?>"><?php echo $data['billing_destination'] ?></option>
<?php } ?>
</select></td>
</td>
</tr>
</table>
</form>

destination_get.php

<?php
require("functions.php");
dbconnect();
$q=$_GET["q"];
$sql="SELECT * FROM destination WHERE id = '".$q."'";
$result = mysqli_query($link,$sql)or die(mysqli_error($link));
echo "<table border='1'>
<tr>
<th>Company Name</th>
<th>Code</th>
<th>Billing Destination</th>
<th>Price</th>
</tr>";
while($row = mysqli_fetch_array($result))
  {
  echo "<tr>";
  echo "<td>" . $row['company_name'] . "</td>";
  echo "<td>" . $row['code_phone'] . "</td>";
  echo "<td>" . $row['billing_destination'] . "</td>";
  echo "<td>" . $row['price'] . "</td>";
   echo "</tr>";
  }
echo "</table>";
?>

Первая проблема:

<option value="<?php echo $data['id'] ?>"><?php echo $data['billing_destination'] ?></option>

Не отображается ничего. Ставлю:

<?php $query=mysqli_query($link,"Select id,billing_destination FROM destination"); ?>

Отображает список, но получаю другую ошибку:

TypeError: document.getElementById(...) is null document.getElementById("txtHint").innerHTML = xmlhttp.responseText;