无刷新PHP+Ajax聊天室实现揭秘

php+ajax打造无刷新聊天室 

主文件，也可以放在一个框架网页中，代码如下：

<script language="javascript">
window.onload=fwrite;
function auto(){
 fwrite("view");
}
function fwrite(act){
 str=document.getElementById("info").value;
 pub=document.getElementById("select").selectedIndex;
 if(act!=='view') document.getElementById("info").value='';
 var xmlhttp = new ActiveXObject("Msxml2.XMLHTTP.5.0");//XMLHTTP.4.0|XMLHTTP.3.0|XMLHTTP
 var url="fwrite.php?action="+act+"&str="+str+"&pub="+pub;//无数据库版
 //var url="dbwrite.php?action="+act+"&au=&info="+str+"&flag="+pub;
 xmlhttp.open("GET",url, false);
 xmlhttp.setRequestHeader("If-Modified-Since","0");//防止缓存
 //xmlhttp.setRequestHeader("Content-Type","text/xml");
 //xmlhttp.setRequestHeader("Content-Type","gb2312");
 xmlhttp.send();
 if(xmlhttp.readyState==4 && xmlhttp.status==200){
  var text=xmlhttp.responseText;
  document.getElementById("content").innerHTML=text;
 }else{
  document.getElementById("content").innerHTML="网络忙，请重试...";
 }
 setTimeout("fwrite('view')",1000);
}
function chang(v,id,color){