function login(){
    $user_login = mysql_real_escape_string($_POST['user_login']);
    $pass_login = mysql_real_escape_string($_POST['pass_login']);
    $submit_login = $_POST['submit_login'];

    $check_username = mysql_query("SELECT * FROM `account` WHERE username='$user_login'");
    $numacc = mysql_num_rows($check_username);

    if ($numacc == 1) {

        $user_login_get_username_and_password = mysql_query("SELECT * FROM `account` WHERE username='$user_login'");
        while ($row = mysql_fetch_array($user_login_get_username_and_password))
            {
                $db_username = $row['username'];
                $db_password = $row['password'];
                $db_id = $row['id'];
            }

        if(isset($submit_login) && strlen($user_login) > 1 && strlen($pass_login) > 1) {
            $pass_hash_login = sha1(strtoupper($user_login).'!'.strtoupper($pass_login));
            if($db_password == $pass_hash_login && strtoupper($db_username) == strtoupper($user_login)) {

                    $_SESSION['username'] = $db_username;
                    $_SESSION['id'] = $db_id;
                    echo '<script type="text/javascript">alert("You are logged in, press OK to continue.");</script>';
                    echo '<script type="text/javascript">window.location = "index.php"</script>';

            }else{
                die ('pass and user do not match');
            }
        }
    }
}