<form action="login.php" method="POST">
<input type="text" name="login">
<input type="password" name="pswd">
<input type="submit" name="enter" value="войти">
</form>

function db_connect()
    {
        $host = "ваш хост(по умолчанию localhost)";
        $user = "ваш логин";
        $pswd = "ваш пароль";
        $db = "ваша бд";
        
        $connection = mysql_connect($host, $user, $pswd);
        mysql_query("SET NAMES utf8");
        if(!$connection || !mysql_select_db($db, $connection))
        {
            return false;
        }
        return $connection;
    }

function check_user($login, $pswd)
    {
        db_connect();
        
        $query = sprintf(" SELECT username FROM users WHERE users.username = '%s' AND users.password = '%s' ",
                        mysql_real_escape_string($login),
                        mysql_real_escape_string($pswd));
                        
        $result = mysql_query($query);
        if(mysql_num_rows($result) > 0) return TRUE;
            else   return FALSE;               
    }

include('db.php');
if(isset($_POST['enter']) && !empty($_POST['login']) && !empty($_POST['pswd']))
    {
        $login = $_POST['login'];
        $pswd = sha1(md5($_POST['pswd']));
        if(check_user($login, $pswd))
        {
            $_SESSION['username'] = $login;
            $_SESSION['status'] = $status['status'];
            header("Location: index.php");
        }
		
        else header("Location: index.php");