HTML

<script>

function createRequestObject() {

var ro;

var browser = navigator.appName;

if(browser == "Microsoft Internet Explorer"){

ro = new ActiveXObject("Microsoft.XMLHTTP");

}else{

ro = new XMLHttpRequest();

}

return ro;

}
var http = createRequestObject();
function sndReq(zip) {

http.open('get', 'zipcode.php?zip='+zip);

http.onreadystatechange = handleResponse;

http.send(null);

}
function handleResponse() {

if(http.readyState == 4){

var response = http.responseText;

var update = new Array();
if(response.indexOf('|' != -1)) {

update = response.split('|');

document.getElementById("city").value = update[0];

document.getElementById("state").value = update[1];

}

}

}

</script>

<h3>Enter A United States Zipcode, Then Tab</h3>

<table align="center">

<tr>

<td>Enter Zipcode:</td>

<td><input type="text" id="zipcode" 
name="zipcode" onBlur="sndReq(this.value);"/></td>

</tr>

<tr>

<td>City:</td>

<td><input type="text" id="city" name="city"/></td>

</tr>

<tr>

<td>State:</td>

<td><input type="text" id="state" name="state"/></td>

</tr>

</table>

<?php

$dbuser = 'root';

$dbpass = '111111';
$cn = mysql_connect("localhost", $dbuser, $dbpass);

$db = mysql_select_db("ajax");
$sql = "select city, state from zipcodes where zipcode 
= " . $_REQUEST['zip'];

$rs = mysql_query($sql);

$row = mysql_fetch_array($rs);
echo $row['city'] . "|" . $row['state'];
mysql_close($cn);

?>

if(response.indexOf('|' != -1)) {

update = response.split('|');

document.getElementById("city").value = update[0];

document.getElementById("state").value = update[1];

}