When i tried my chatbox in my html website a warnings appeared.
Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/bitmsfgx/public_html/chat/index.php:8) in /home/bitmsfgx/public_html/chat/index.php on line 10
Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/bitmsfgx/public_html/chat/index.php:8) in /home/bitmsfgx/public_html/chat/index.php on line 10
index.php
<!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>
<title>Chat</title>
<link type="text/css" rel="stylesheet" href="style.css" />
</head>
 <?
@ob_start();
session_start();
function loginForm(){
    echo'
    <div id="loginform">
    <form action="index.php" method="post">
        <p>Please enter your name to continue:</p>
        <label for="name">Name:</label>
        <input type="text" name="name" id="name" />
        <input type="submit" name="enter" id="enter" value="Enter" />
    </form>
    </div>
    ';
}
if(isset($_POST['enter'])){
    if($_POST['name'] != ""){
        $_SESSION['name'] = stripslashes(htmlspecialchars($_POST['name']));
    }
    else{
        echo '<span class="error">Please type in a name</span>';
    }
}
?>
<?php
if(!isset($_SESSION['name'])){
    loginForm();
}
else{
?>
<div id="wrapper">
    <div id="menu">
        <p class="welcome">Welcome, <b><?php echo $_SESSION['name']; ?></b></p>
        <p class="logout"><a id="exit" href="#">Exit Chat</a></p>
        <div style="clear:both"></div>
    </div>    
    <div id="chatbox"></div>
    <form name="message" action="">
        <input name="usermsg" type="text" id="usermsg" size="63" />
        <input name="submitmsg" type="submit"  id="submitmsg" value="Send" />
    </form>
</div>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js"></script>
<script type="text/javascript">
// jQuery Document
$(document).ready(function(){
    //If user submits the form
    $("#submitmsg").click(function(){   
        var clientmsg = $("#usermsg").val();
        $.post("post.php", {text: clientmsg});              
        $("#usermsg").attr("value", "");
        return false;
    });
    //Load the file containing the chat log
    function loadLog(){     
        $.ajax({
            url: "log.html",
            cache: false,
            success: function(html){        
                $("#chatbox").html(html); //Insert chat log into the #chatbox div               
            },
        });
    }
    //Load the file containing the chat log
    function loadLog(){     
        var oldscrollHeight = $("#chatbox").attr("scrollHeight") - 20; //Scroll height before the request
        $.ajax({
            url: "log.html",
            cache: false,
            success: function(html){        
                $("#chatbox").html(html); //Insert chat log into the #chatbox div   
                //Auto-scroll           
                var newscrollHeight = $("#chatbox").attr("scrollHeight") - 20; //Scroll height after the request
                if(newscrollHeight > oldscrollHeight){
                    $("#chatbox").animate({ scrollTop: newscrollHeight }, 'normal'); //Autoscroll to bottom of div
                }               
            },
        });
    }
    setInterval (loadLog, 2500);    //Reload file every 2500 ms or x ms if you w
});
</script>
<?php
}
?>
<script type="text/javascript">
// jQuery Document
$(document).ready(function(){
    //If user wants to end session
    $("#exit").click(function(){
        var exit = confirm("Are you sure you want to end the session?");
        if(exit==true){window.location = 'index.php?logout=true';}      
    });
});
</script>
<?php 
if(isset($_GET['logout'])){ 
    //Simple exit message
    $fp = fopen("log.html", 'a');
    fwrite($fp, "<div class='msgln'><i>User ". $_SESSION['name'] ." has left the chat session.</i><br></div>");
    fclose($fp);
    session_destroy();
    header("Location: index.php"); //Redirect the user
}
?>
</body>
</html>
post.php
<?
@ob_start();
session_start();
if(isset($_SESSION['name'])){
    $text = $_POST['text'];
    $fp = fopen("log.html", 'a');
    fwrite($fp, "<div class='msgln'>(".date("g:i A").") <b>".$_SESSION['name']."</b>: ".stripslashes(htmlspecialchars($text))."<br></div>");
    fclose($fp);
}
?>
style.css
/* CSS Document */
body {
    font:12px arial;
    background-color: #ffffff !important;
    text-align:center;
    padding:35px; }
form, p, span {
    margin:0;
    padding:0; }
input { font:12px arial; }
a {
    color:#0000FF;
    text-decoration:none; }
    a:hover { text-decoration:underline; }
#wrapper, #loginform {
    margin:0 auto;
    padding-bottom:25px;
    background:#EBF4FB;
    width:504px;
    border:1px solid #ACD8F0; }
#loginform { padding-top:18px; }
    #loginform p { margin: 5px; }
#chatbox {
    text-align:left;
    margin:0 auto;
    margin-bottom:25px;
    padding:10px;
    background:#fff;
    height:270px;
    width:430px;
    border:1px solid #ACD8F0;
    overflow:auto; }
#usermsg {
    width:395px;
    border:1px solid #ACD8F0; }
#submit { width: 60px; }
.error { color: #ff0000; }
#menu { padding:12.5px 25px 12.5px 25px; }
.welcome { float:left; }
.logout { float:right; }
.msgln { margin:0 0 2px 0; }
 
    