if(isset($_POST['login'])){

 $username = $_POST['username'];
$password = $_POST['password'];
 $pc = md5($password);

$req = $pdo->prepare('SELECT * FROM users WHERE nom= :username AND pass= :password');
$req->execute(array(
    'username' => $username,
    'password' => $pc,
    ));

 if ($user = $req->fetch()) {
    $_SESSION['auth'] = $user;
    header("location:home.php");
    exit();

 }

 else{
 echo"<script> alert('LE NOM D UTILISATEUR OU LE MOTS DE PASSE INCORRECTE')</script>";
}