Voici pour le code
ceci est le script qui rassemblera les deux chat php :
<?php 
<html>
 <link href="./style2.css" rel="stylesheet" type="text/css" />
	<head>
	</head>
			<body>
			
						<div id="menu_fond">
							
							<? include('chat1/chat_client_1.php'); ?>
						
						</div>
						
						<div id="cadre">
							
							<? include('chat2/chat_client_2.php'); ?>
					
						</div>
			</body>
</html>
 php ?>
Et voici le code de mon premier chat :
<?<?php
function createForm1()
{
?>
      <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
        <table align="center">
          <tr><td colspan="2">  </td></tr>
          <tr><td>Votre prénom : </td>
          <td><input class="text" type="text" name="name" /></td></tr>
          <tr><td colspan="2" align="center">
             <input class="text" type="submit" name="submitBtn" value="Login" />
          </td></tr>
        </table>
      </form>
<?php
}
if (isset($_GET['u']))
{
   unset($_SESSION['nickName1']);
}
// Gestion Du pseudo 
if (isset($_POST['submitBtn']))
{
      $name    = isset($_POST['name']) ? $_POST['name'] : "Profil";
      $_SESSION['nickName1'] = $name;
}
$nickName1 = isset($_SESSION['nickName1']) ? $_SESSION['nickName1'] : "Caché";   
?>
<html>
<head>
   <title>Chat  </title>
   <link href="style/style.css" rel="stylesheet" type="text/css" />
    <script language="javascript" type="text/javascript">
	
      var httpObject1 = null;
      var link1 = "";
      var timerID1 = 0;
      var nickName1 = "<?php echo $nickName1; ?>";
      function gethttpObject1()
	  {
         if (window.ActiveXObject) return new ActiveXObject("Microsoft.XMLHTTP");
         else if (window.XMLHttpRequest) return new XMLHttpRequest();
         else 
		 {
            alert("Votre navigateur ne supporte pas l'AJAX.");
            return null;
         }
      }   
      function setOutput1()
	  {
         if(httpObject1.readyState == 4)
		 {
            var response1 = httpObject1.responseText;
            var objDiv1 = document.getElementById("result");
            objDiv1.innerHTML += response1;
            objDiv1.scrollTop = objDiv1.scrollHeight;
            var inpObj1 = document.getElementById("msg");
            inpObj1.value = "";
            inpObj1.focus();
         }
      }
      function setAll1()
	  {
         if(httpObject1.readyState == 4)
		 {
            var response1 = httpObject1.responseText;
            var objDiv1 = document.getElementById("result");
            objDiv1.innerHTML = response1;
            objDiv1.scrollTop = objDiv1.scrollHeight;
         }
      }
        
      function doWork1()
	  {    
         httpObject1 = gethttpObject1();
         if (httpObject1 != null) 
		 {
            link1 = "message_1.php?nick="+nickName1+"&msg="+document.getElementById('msg').value;
            httpObject1.open("GET", link1 , true);
            httpObject1.onreadystatechange = setOutput1;
            httpObject1.send(null);
         }
      }
        
      function doReload1()
	  {    
         httpObject1 = gethttpObject1();
         var randomnumber=Math.floor(Math.random()*10000);
         if (httpObject1 != null) 
		 {
            link1 = "message_1.php?all=1&rnd="+randomnumber;
            httpObject1.open("GET", link1 , true);
            httpObject1.onreadystatechange = setAll1;
            httpObject1.send(null);
         }
      }
      function UpdateTimer1() 
	  {
         doReload1();   
         timerID1 = setTimeout("UpdateTimer1()", 5000);
      }
	  
  
    </script>   
</head>
<body onload="UpdateTimer1();">
    <div id="main">
      <div id="caption">Chat</div>
      <div id="icon"> </div>
<?php 
if (!isset($_SESSION['nickName1']) )
{ 
    createForm1();
} else  
	{ 
      $name1    = isset($_POST['name1']) ? $_POST['name1'] : "Unnamed";
      $_SESSION['nickName1'] = $name1;
	 ?>
      
     <div id="result">
     <?php 
          $data1= file("msg_1.html");
        foreach ($data1 as $line1) 
		{
        	echo $line1;
        } 
	  
	 ?>
	 
      </div>
      <div id="sender" >
         Votre message: <input type="text" name="msg" size="30" maxlength="50" id="msg" />
         <button onclick="doWork1();">Ecrire</button>
      </div>   
	 
<?php 
    }
	
?>
    </div>
</body>     ?>
et voici le code qui envoie le message:
<?php 
IF (!ISSET($_SESSION)) 
	{
		SESSION_START();
	}
		if ( empty($_GET['msg']) )
		{ 
		} 
		else
		{
		
		}	
		
				$_SESSION['last_session_request'] = TIME();
				if (isset($_GET['msg']))
					{
					if (file_exists('msg_1.html')) 
					{
		  		 $f1 = fopen('msg_1.html',"a+");
					} else 
					{
					   $f1 = fopen('msg_1.html',"w+");
					}
			 
		
				  $nick = isset($_GET['nick']) ? $_GET['nick'] : "Hidden";
				  $msg  = isset($_GET['msg']) ? htmlspecialchars($_GET['msg']) : ".";
				  $line1 = "<p><span class=\"name\">$nick: </span><span class=\"txt\">$msg</span></p>";
					fwrite($f1,$line1."\r\n");
					fclose($f1);
					
					echo $line1;
					
				} else if (isset($_GET['all'])) 
				
				{
				   $flag1 = file('msg_1.html');
				   $content1 = "";
				   foreach ($flag1 as $value) 
				   {
					$content1 .= $value;
				   }
				   echo $content1;
				}
			
?>	
j'ai le même code pour le deuxième chat j'ai juste renommé les variables et fonctions de celui ci avec un 1 derrière pour pas qu'il y est de problème en vain le problème et toujours présent