<form id="formconnexion" method="post" action="page2.php">
                <div class="server-info" id="resultat">Connectez-vous !</div>
                <div class="server-info">identifiant&nbsp;
                	<input type="text" name="login" id="login2" style="font-size: smaller; width: 70px;" value=""/></div>
                <div class="server-info">Mot de passe&nbsp;
                	<input type="password" name="pass" id="password2" style="font-size: smaller; width: 70px;" value=""/>
                    <!--<input type="submit" name="connexion" value="Connexion" onchange="go()"/>-->
                    <input type="button" name="connexion" value="Connexion" onclick="go()"/>
                </div>
                <a href="#" class="button red" title="Logout">
                    <span class="smaller">LOGOUT</span></a>
            </form>

<script type="text/javascript">
 
    function getXMLHttpRequest() {
    	var xhr = null;
    	
    	if (window.XMLHttpRequest || window.ActiveXObject) {
    		if (window.ActiveXObject) {
    			try {
    				xhr = new ActiveXObject("Msxml2.XMLHTTP");
    			} catch(e) {
    				xhr = new ActiveXObject("Microsoft.XMLHTTP");
    			}
    		} else {
    			xhr = new XMLHttpRequest(); 
    		}
    	} else {
    		alert("Votre navigateur ne supporte pas l'objet XMLHTTPRequest...");
    		return null;
    	}    	
    	return xhr;
    }   
 
function go(){
var xhr = getXMLHttpRequest();		xhr.onreadystatechange = function(){		if(xhr.readyState == 4 && xhr.status == 200){	txtAafficher = xhr.responseText;				document.getElementById('resultat').innerHTML = txtAafficher;
				alert(txtAafficher);
}
else {				alert('There was a problem with the request.');
	}
}
			xhr.open("POST","page.php",true);
			xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');

var argLogin = encodeURIComponent(document.getElementById('login2').value);
var argPass = encodeURIComponent(document.getElementById('password2').value);
				var data = "login=" + argLogin + "&pwd" + argPass;
			xhr.send(data);			
	}     
    </script>

<?php

header("Content-Type: text/plain");

$login = $_POST['login'];
$pass = $_POST['pass'];
// je teste si le fomulaire à été envoyé
    if (isset($_POST['connexion']) && $_POST['connexion'] == 'Connexion') {
        if ((isset($_POST['login']) && !empty($_POST['login']))
            && (isset($_POST['pass']) && !empty($_POST['pass']))){

            // connexion à la base
            $base = mysql_connect('localhost','root','');
            mysql_select_db('base', $base);
// construction de la requete
            /*$sql = 'SELECT count(*)
                        FROM membre
                        WHERE login="'.$login.'"
                        AND pass_md5="'.$pass.'"';  */

            $sql = 'SELECT count(*)
            FROM membre
            WHERE login="'.$_POST['login'].'"
            AND pass_md5="'.$_POST['pass'].'"';

            $requete = mysql_query($sql) or die('erreur !!!'.$sql.'<br>'.mysql_error());
            $resultat = mysql_fetch_array($requete);

            if(mysql_num_rows($resultat) == 1){
                echo "Bonjour " . $login ;
            }
            else {
              echo "Inscrivez-vous !!";
            }
        }
        else {
            echo = 'Au moins 1 champ vide';
        }
    }
?>

<?php

	header("Content-Type: text/plain");
	
	$login 	= (isset($_POST["login"])) 	? $_POST["login"] 	: NULL;
	$pass 	= (isset($_POST["pass"])) 	? $_POST["pass"] 	: NULL;
	
	if ($login && $pass) {
		echo "Bonjour " . $login ;
	} else {
		echo "FAIL";
	}
?>