Script Espace Membre !!

<?php
session_start();
$login = $_POST['login'];
$mdp = $_POST['mdp'];

$sql = mysql_query('SELECT * FROM login WHERE login = "'.$login.'"');
if ($data = mysql_fetch_array($sql)) {
   if ($data['mdp'] == $mdp) {
        $_SESSION['login'] = $data['login'];
        $_SESSION['prenom'] = $data['prenom'];
        echo 'Vous etes connectés';
   }
   else {
        echo 'mot de passe incorrect'
   }
}
else {
echo 'login incorrect';
}
?>

<?php
session_start();
echo 'Bonjour '.$_SESSION['login'].' Tu t\'appel : '.$_SESSION['prenom'];
?>