传说中的comet（ajax版）？

不知道这是不是就是传说中的comet，感觉和普通的ajax没什么区别。也许这并不是，也许只是后台代码的区别。

demo下载：comet-ajax.zip

HTML代码：

<div id="content">
</div>

<p>
  <form action="" method="get">
    <input type="text" name="word" id="word" value="" />
    <input type="button" id="send" name="send" value="Send" />
    <input type="button" id="stop" name="stop" value="stop" />
  </form>
</p>

JS代码（用的jquery）：

var Comet = function(options){
    this.init(options);
};
Comet.prototype = {
    constructor: Comet,
    init:function(options){
        this.options = {
            url:"",
            callback:function(){}
        }
        this.options = $.extend(this.options,options||{});
        this.url = this.options.url;
        this.callback = this.options.callback;
        this.timestamp = 0;
        this.noerror = true;
        this.lock = true;
    },
    connect: function(){
        this.lock = false;
        this.ajaxLoop();
    },
      disconnect: function(){
        this.lock = true;
    },
    ajaxLoop: function(){
        if(this.url && !this.lock){
            var _this = this;
            $.ajax({
                url:_this.url,
                type:'get',
                data:'timestamp=' + _this.timestamp,
                dataType:'json',
                cache:false,
                success:function(json){
                    _this.timestamp = json['timestamp'];
                    _this.handleResponse(json);
                    _this.noerror = true;
                },
                complete:function(){
                    if (_this.noerror){
                        _this.ajaxLoop();
                    }else{
                        // if a connection problem occurs, try to reconnect each 5 seconds
                        setTimeout(function(){_this.ajaxLoop()}, 5000); 
                    }
                    _this.noerror = false;
                }
            })
        }
    },
      handleResponse: function(response){
        this.callback(response);
      },

    doRequest: function(request){
        if(this.url && !this.lock){
            $.get(this.url, { 'msg': request } ); 
        }
    }
}
var comet = new Comet({
    url:'./backend.php',
    callback:function(response){
        $('#content').append('<div>' + response['msg'] + '</div>');
    }
});
comet.connect();
$("#send").click(function(){
    comet.doRequest($('#word').val());
    $('#word').val('');
})
$("#stop").click(function(){
    comet.disconnect();
})

php代码：

<?php

$filename  = dirname(__FILE__).'/data.txt';

// store new message in the file
$msg = isset($_GET['msg']) ? $_GET['msg'] : '';
if ($msg != '')
{
  file_put_contents($filename,$msg);
  die();
}

// infinite loop until the data file is not modified
$lastmodif    = isset($_GET['timestamp']) ? $_GET['timestamp'] : 0;
$currentmodif = filemtime($filename);
while ($currentmodif <= $lastmodif) // check if the data file has been modified
{
  usleep(10000); // sleep 10ms to unload the CPU
  clearstatcache();
  $currentmodif = filemtime($filename);
}

// return a json array
$response = array();
$response['msg']       = file_get_contents($filename);
$response['timestamp'] = $currentmodif;
echo json_encode($response);
flush();

?>