Hi, I am a PHP newbie and need some help with this storelocator I am building.

I would like to user to select the county they would like to find store located in by using a drop down menu.

this is the html and AJAX for the user interface
HTML Code:
<html>
<head>
<script type="text/javascript">
function showUser(str)
{
if (str=="")
  {
  document.getElementById("txtHint").innerHTML="";
  return;
  }
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","getuser.php?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>

<form>
<select name="shop" onchange="showUser(this.value)">
<option value="">Select a County/Region:</option>
<option value="1">West Midlands</option>
<option value="2">East Midlands</option>
<option value="3">South West</option>
<option value="4">South East</option>
<option value="5">The North</option>
<option value="6">Scotland</option>
<option value="7">Wales</option>
<option value="8">London</option>
<option value="9">Herefordshire</option>
</select>
</form>
<br />
<div id="txtHint"><b>Try one of these outlets or shops</b></div>

</body>
</html>
I have a table called store in mySQL db with the following fields: company_name, address, county, country, phone, web_site.

I would like the user to be able to select e.g. "Herefordshire" and all shops with county = Herefordshire should be displayed. This is the page for the php operation:

PHP Code:
<?php
$q=$_GET["q"];

$con = mysql_connect('localhost', 'shops', 'pwds123');
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }

mysql_select_db("shops", $con);

$sql="SELECT * FROM shop WHERE county = '".$q."'";

$result = mysql_query($sql);

echo "<table border='1'>
<tr>
<th>Company Name</th>
<th>Address</th>
<th>City/Town</th>
<th>County</th>
<th>Post Code</th>
<th>Phone</th>
<th>Web Site</th>
</tr>";

while($row = mysql_fetch_array($result))
  {
  echo "<tr>";
  echo "<td>" . $row['company_name'] . "</td>";
  echo "<td>" . $row['address'] . "</td>";
  echo "<td>" . $row['city_town'] . "</td>";
  echo "<td>" . $row['county'] . "</td>";
  echo "<td>" . $row['post_code'] . "</td>";
   echo "<td>" . $row['phone'] . "</td>";
    echo "<td>" . $row['web_site'] . "</td>";
  echo "</tr>";
  }
echo "</table>";

mysql_close($con);
?>
The above doesn't pull any data - which I assume it because I don't know how to set up the query properly.
The reason I am using AJAX on the html script is because I found an example on the web but I realise it might not be the best way but am not capable to determine that.

Appreciate any help or nudge in the right direction. As I said, am a newbie so need some detailed help.