在customer.php的文件中，代码如下：
<html>
<head>
<script type="text/javascript">
function showCustomer(str)
{
var xmlhttp;
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","/test/getcustomer.php?q="+str,true);//这里的url是指你的文件路径，例如，我的customer.php和getcustomer.php都在www下的test文件 目录下，所以就写成了此种形式
xmlhttp.send();
}
</script>
</head>
<body>
<form action="" style="margin-top:15px;">
<label>请选择一位客户：
<select name="customers" onchange="showCustomer(this.value)" style="font-family:Verdana, Arial, Helvetica, sans-serif;">
<option value="APPLE">Apple Computer, Inc.</option>
<option value="BAIDU ">BAIDU, Inc</option>
<option value="Canon">Canon USA, Inc.</option>
<option value="Google">Google, Inc.</option>
<option value="Nokia">Nokia Corporation</option>
<option value="SONY">Sony Corporation of America</option>
</select>
</label>
</form>
<br />
<div>客户信息将在此处列出 ...</div>
<div id="txtHint"></div>
</body>
</html>
在getcustomer.php的文件中，代码如下：
<?php
$q=$_GET["q"];
$con = mysql_connect(‘localhost‘, ‘root‘, ‘root‘);
if (!$con)
{
die(‘Could not connect: ‘ . mysql_error());
}
mysql_select_db("test", $con);
$sql="SELECT * FROM user1 WHERE firstname= ‘".$q."‘";
//var_dump($sql);
$result = mysql_query($sql);
echo "<table border=‘1‘>
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Age</th>
<th>Hometown</th>
<th>Job</th>
</tr>";
while($row = mysql_fetch_array($result))
{
echo "<tr>";
echo "<td>" . $row[‘firstname‘] . "</td>";
echo "<td>" . $row[‘lastname‘] . "</td>";
echo "<td>" . $row[‘age‘] . "</td>";
echo "<td>" . $row[‘hometown‘] . "</td>";
echo "<td>" . $row[‘Job‘] . "</td>";
echo "</tr>";
}
echo "</table>";
mysql_close($con);
?>
//数据库是test， 表是user1，一共有五个字段，分别是firstname，lastname，age，hometown和Job
最后能实现页面无刷新字段的变化的效果！刚学Ajax，感觉很不错！