与ajax初见

<script type="text/javascript">
            window.onload = function(){
                document.getElementById('btn').onclick=function(){
                    //创建ajax对象
                    var req = new XMLHttpRequest();
                    //get请求到服务器
                    req.open('get','ajax.php');
                    //发送请求
                    req.send();
                }
            }
        </script>
        <input type="submit" name="" id="btn" value="点击按钮" />

先是创建对象var req = new XMLHttpRequest();,然后请求到服务器open(),最后send();发送请求完成。

<?php
$fp = fopen('test.txt','a');
$time = date('Y-m-d H:i:s'."\n");
fputs($fp,$time);

执行服务器的代码;