在注册和登录时对密码进行加密

我在我的网站上设置了注册系统，当用户注册时，密码是他们注册的电子邮件和密码的md5混合。不幸的是，我无法让它正常工作。这是代码：

注册时：

$user = strip_tags(substr($_POST['email'],0,32));
$pass = strip_tags(substr($_POST['password'],0,32));
$cleanPass = crypt(md5($pass),md5($user));
$date = time();
$stmt = $db->prepare("INSERT INTO users (password, email, first, last, date)
        VALUES(:password, :email, :first, :last, :date)");

登录时：

$email = $_POST['email'];
$user = strip_tags(substr($_POST['email'],0,32));
$pass = strip_tags(substr($_POST['password'],0,32));        
$cleanPass = crypt(md5($pass),md5($user));
$stmt = $db->prepare("SELECT email,password FROM users WHERE email=:email AND password=:password limit 1");