php+ajax实现无刷新动态加载数据技术

<?php 
require_once('connect.php'); 
$user = array('demo1','demo2','demo3','demo3','demo4'); 
?> 
<div id="container"> 
  <?php 
  $query=mysql_query("select * from say order by id desc limit 0,15"); 
  while ($row=mysql_fetch_array($query)) { 
  ?> 
  <div class="single_item"> 
    <div class="element_head"> 
       <div class="date"><?php echo date('m-d H:i',$row['addtime']);?></div> 
       <div class="author"><?php echo $user[$row['userid']];?></div> 
     </div> 
     <div class="content"><?php echo $row['content'];?></div> 
  </div> 
  <?php } ?> 
 </div> 
<div class="nodata"></div> 

$(window).scroll(function () { 
  var pageH = $(document.body).height(); //页面总高度 
  var scrollT = $(window).scrollTop(); //滚动条top 
  var aa = (pageH-winH-scrollT)/winH; 
}); 

if(aa<0.02){ 
  $.getJSON("result.php",{page:i},function(json){ 
    ..... 
  }); 
 } 

if(json){ 
  var str = ""; 
  $.each(json,function(index,array){ //遍历 
    var str = "..."; //获取的JSON数据 
    $("#container").append(str); //追加 
  }); 
  i++; //页数+1 
}else{ 
  $(".nodata").show().html("别滚动了，已经到底了。。。"); 
  return false; 
} 

$(function(){ 
  var winH = $(window).height(); //页面可视区域高度 
  var i = 1; //设置当前页数 
  $(window).scroll(function () { 
    var pageH = $(document.body).height(); 
    var scrollT = $(window).scrollTop(); //滚动条top 
    var aa = (pageH-winH-scrollT)/winH; 
    if(aa<0.02){ 
      $.getJSON("result.php",{page:i},function(json){ 
        if(json){ 
          var str = ""; 
          $.each(json,function(index,array){ 
            var str = "<div class=\"single_item\"><div class=\"element_head\">"; 
            var str += "<div class=\"date\">"+array['date']+"</div>"; 
            var str += "<div class=\"author\">"+array['author']+"</div>"; 
            var str += "</div><div class=\"content\">"+array['content']+"</div></div>"; 
            $("#container").append(str); 
          }); 
          i++; 
        }else{ 
          $(".nodata").show().html("别滚动了，已经到底了。。。"); 
          return false; 
        } 
      }); 
    } 
  }); 
}); 

require_once('connect.php'); //连接数据库 
 
$user = array('demo1','demo2','demo3','demo3','demo4'); 
$page = intval($_GET['page']); //获取请求的页数 
$start = $page*15; 
$query=mysql_query("select * from say order by id desc limit $start,15"); 
while ($row=mysql_fetch_array($query)) { 
  $arr[] = array( 
    'content'=>$row['content'], 
    'author'=>$user[$row['userid']], 
    'date'=>date('m-d H:i',$row['addtime']) 
  ); 
} 
echo json_encode($arr); //转换为json数据输出