php+xml结合Ajax实现点赞功能完整实例

<?xml version="1.0"?> 
<goodtree> 
  <goodnode> 
    <id>0</id> 
    <count>17</count> 
  </goodnode> 
  <goodnode> 
    <id>1</id> 
    <count>37</count> 
  </goodnode> 
  <goodnode> 
    <id>2</id> 
    <count>67</count> 
  </goodnode>   
</goodtree>

<div id="goodcount">
  <span>0</span><button onclick="goodplus(0);">good+1</button>
  <span>0</span><button onclick="goodplus(1);">good+1</button>
  <span>0</span><button onclick="goodplus(2);">good+1</button>
  <span>0</span><button onclick="goodplus(3);">good+1</button>
</div>

var span = document.getElementsByTagName('span'); 
var num; 
var flag = 0; 

for(var i = 1; i < span.length + 1; i++){ 
    senddata(i);   
} 

function goodplus(gindex){ 
    flag = 1; 
    num = parseInt(span.item(gindex).innerHTML); 
    if(checkcookie(gindex) == true){ 
      num = num + 1; 
      senddata(gindex); 
    }else{ 
      alert("你已经点过赞咯！")   
    } 
} 

function senddata(aindex){ 
    var xmlhttp; 
    var txt; 
    if(window.XMLHttpRequest){ 
      xmlhttp=new XMLHttpRequest(); 
    }else{ 
      xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); 
    } 
    xmlhttp.onreadystatechange=function(){ 
      if(xmlhttp.readyState == 4 && xmlhttp.status == 200){ 
        if(flag == 0){ 
          xmldoc = xmlhttp.responseXML; 
          var count = xmldoc.getElementsByTagName('count'); 
          var span2 = document.getElementsByTagName('span'); 
          for(var j = 0; j < count.length; j++){ 
            span2.item(j).innerHTML = count[j].childNodes[0].nodeValue; 
          } 
        }else if(flag == 1){ 
          xmldoc2 = xmlhttp.responseText; 
          var span3 = document.getElementsByTagName('span'); 
          span3.item(aindex).innerHTML = xmldoc2; 
        } 
      } 
    } 
    if(flag == 0){ 
      xmlhttp.open("GET","/ajax/foodmap/index.xml"); 
    }else{ 
      xmlhttp.open("GET","/ajax/foodmap/index.php?num=" + num + "&aindex=" + aindex,true);   
    } 
    xmlhttp.send(); 
} 

//判断是否已经存在了cookie 
function checkcookie(gindex){ 
    var thiscookie = 'sdcity_foodmap_goodplus' + gindex; 
    var mapcookie = getCookie(thiscookie) 
    if (mapcookie!=null && mapcookie!=""){ 
      return false; 
    }else { 
      setCookie(thiscookie,thiscookie,365); 
      return true; 
    }   
}

//获取cookie 
function getCookie(c_name){
//获取cookie，参数是名称。 
    if (document.cookie.length > 0){
//当cookie不为空的时候就开始查找名称  
      c_start = document.cookie.indexOf(c_name + "="); 
      if (c_start != -1){
//如果开始的位置不为-1就是找到了、找到了之后就要确定结束的位置 
        c_start = c_start + c_name.length + 1 ;
//cookie的值存在名称和等号的后面，所以内容的开始位置应该是加上长度和1 
        c_end = document.cookie.indexOf(";" , c_start); 
        if (c_end == -1) { 
          c_end = document.cookie.length; 
        } 
        return unescape(document.cookie.substring(c_start , c_end));
//返回内容，解码。 
      }  
    } 
    return ""; 
} 

//设置cookie 
function setCookie(c_name,value,expiredays){
//存入名称，值，有效期。有效期到期事件是今天+有效天数。然后存储cookie， 
    var exdate=new Date(); 
    exdate.setDate( exdate.getDate() + expiredays ) 
    document.cookie = c_name + "=" + escape(value) + ((expiredays==null) ? "" : "; expires=" + exdate.toGMTString()) 
} 

<?php 
$num = $_GET['num']; 
echo $_GET['num']; 
$aindex = $_GET['aindex']; 
$dom=new DOMDocument('1.0'); 
$dom->load('index.xml'); 
$goodnode=$dom->getElementsByTagName('goodnode'); 
$goodnode = $goodnode->item($aindex); 
$items = $goodnode->getElementsByTagName('count'); 
foreach($items as $a){ 
  $a->nodeValue = $_GET['num']; 
} 
$dom->save('index.xml'); 
?>