实现一个简单的服务端推送方案-实例篇Polling

来源：互联网发布：breed mac修改编辑：程序博客网时间：2024/06/05 19:38

前面讲过一篇《实现一个简单的服务端推方案》，这里讲实现的实例。

这篇讲Polling，即浏览器客户端长轮循，后端PHP短轮循数据库，功能是从数据库表读取最新的记录并显示。

客户端代码，JS库为prototype.js：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><title>无标题文档</title><script language="JavaScript" type="text/javascript" src="./prototype.js"></script></head><body>  <script language="JavaScript">     var Class = {      create: function() {        return function() {          this.initialize.apply(this, arguments);        }      }    }      var Comet = Class.create();    Comet.prototype = {        maxvid: 0,        url: './backend.php',        noerror: true,        initialize: function(){        },        connect: function(){            this.ajax = new Ajax.Request(this.url, {                method: 'get',                parameters: {                    'maxvid': this.maxvid                },                onSuccess: function(transport){                    var response = transport.responseText.evalJSON();                    this.comet.maxvid = response['vid'];                    this.comet.handleResponse(response);                    this.comet.noerror = true;                },                onComplete: function(transport){                   if (!this.comet.noerror) setTimeout(function(){                                             comet.connect()                                             }, 5000);                    else                     this.comet.connect();                    this.comet.noerror = false;                }            });            this.ajax.comet = this;        },        handleResponse: function(response){            $('content').innerHTML += '<div>' + response['msg'] + '</div>';       }    }    var comet = new Comet();    comet.connect();  </script><div id="content"></div>    </body></html>

服务器PHP代码：backend.php

<?phpheader("Cache-Control: no-cache, must-revalidate");header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");flush();//控制浏览器前端不要缓存结果，每次都要重新查询$maxvid = $_GET["maxvid"];error_log(date("[Y-m-d H:i:s]")." > "."maxvid: ".$maxvid."\n", 3 , "/usr/local/apache2219/logs/php_log");$dblnk = mysql_pconnect('192.168.2.162:3306', 'root', 'cpyf');mysql_select_db('app_m1p', $dblnk);if ( $maxvid <= 0 ) {  $result = mysql_query("select max(vid) from vdooropen");  $result = mysql_fetch_row($result);  $maxvid = $result[0];}while (1){  $result = mysql_query("select * from vdooropen where vid > $maxvid order by vid desc limit 1");  $num = mysql_num_rows($result);  //echo $num;  if ( $num > 0 ) break;  usleep(10000); // sleep 10ms to unload the CPU}$result = mysql_fetch_row($result);// 返回 JSON 数组$response = array();$response['vid'] = $result[0];$response['msg'] = $result[0].",".$result[1].",".$result[2].",".$result[3].",".$result[4];$responseText = json_encode($response);error_log(date("[Y-m-d H:i:s]")." < ".$responseText."\n", 3 , "/usr/local/apache2219/logs/php_log");echo $responseText;flush();?>