PHP chat room application implementation method ideas

//

// Set Chat Message

//

function set_chat_msg()

{

    if(typeof XMLHttpRequest != "undefined")

    {

        oxmlHttpSend = new XMLHttpRequest();

    }

    else if (window.ActiveXObject)

    {

       oxmlHttpSend = new ActiveXObject("Microsoft.XMLHttp");

    }

    if(oxmlHttpSend == null)

    {

       alert("Browser does not support XML Http Request");

       return;

    }

    var url = "chat_send_ajax.php";

    var strname="noname";

    var strmsg="";

    if (document.getElementById("txtname") != null)

    {

        strname = document.getElementById("txtname").value;

        document.getElementById("txtname").readOnly=true;

    }

    if (document.getElementById("txtmsg") != null)

    {

        strmsg = document.getElementById("txtmsg").value;

        document.getElementById("txtmsg").value = "";

    }

    url += "?name=" + strname + "&msg=" + strmsg;

    oxmlHttpSend.open("GET",url,true);

    oxmlHttpSend.send(null);

}

require_once('dbconnect.php');

db_connect();

$msg = $_GET["msg"];

$dt = date("Y-m-d H:i:s");

$user = $_GET["name"];

$sql="INSERT INTO chat(USERNAME,CHATDATE,MSG) " .

      "values(" . quote($user) . "," .

      quote($dt) . "," . quote($msg) . ");";

      echo $sql;

$result = mysql_query($sql);

if(!$result)

{

    throw new Exception('Query failed: ' . mysql_error());

    exit();

}

var t = setInterval(function(){get_chat_msg()},5000);

//

// General Ajax Call

//

var oxmlHttp;

var oxmlHttpSend;

function get_chat_msg()

{

    if(typeof XMLHttpRequest != "undefined")

    {

        oxmlHttp = new XMLHttpRequest();

    }

    else if (window.ActiveXObject)

    {

       oxmlHttp = new ActiveXObject("Microsoft.XMLHttp");

    }

    if(oxmlHttp == null)

    {

        alert("Browser does not support XML Http Request");

       return;

    }

    oxmlHttp.onreadystatechange = get_chat_msg_result;

    oxmlHttp.open("GET","chat_recv_ajax.php",true);

    oxmlHttp.send(null);

}

require_once('dbconnect.php');

db_connect();

$sql = "SELECT *, date_format(chatdate,'%d-%m-%Y %r')

as cdt from chat order by ID desc limit 200";

$sql = "SELECT * FROM (" . $sql . ") as ch order by ID";

$result = mysql_query($sql) or die('Query failed: ' . mysql_error());

// Update Row Information

$msg="";

while ($line = mysql_fetch_array($result, MYSQL_ASSOC))

{

   $msg = $msg . "" .

        "" .

        "";

}

$msg=$msg . "<table style="color: blue; font-family: verdana, arial; " .

  "font-size: 10pt;" border="0">

  <tbody><tr><td>" . $line["cdt"] .

  " </td><td>" . $line["username"] .

  ": </td><td>" . $line["msg"] .

  "</td></tr></tbody></table>";

echo $msg;

function get_chat_msg_result(t)

{

    if(oxmlHttp.readyState==4 || oxmlHttp.readyState=="complete")

    {

        if (document.getElementById("DIV_CHAT") != null)

        {

            document.getElementById("DIV_CHAT").innerHTML =  oxmlHttp.responseText;

            oxmlHttp = null;

        }

        var scrollDiv = document.getElementById("DIV_CHAT");

        scrollDiv.scrollTop = scrollDiv.scrollHeight;

    }

}

create table chat( id bigint AUTO_INCREMENT,username varchar(20),

chatdate datetime,msg varchar(500), primary key(id));