if (isset($_POST['user']) && isset($_POST['pass'])){

        $user = htmlspecialchars($_POST['user']);
        $pass = htmlspecialchars($_POST['pass']);

        if ($user == "" || $pass =="" || $user == " " || $pass ==" ")
        {
            echo "fail - Empty user or pass";
            return;
        }else{

            $query = mysqli_query($link, "SELECT * FROM accounts WHERE username ='$user' AND password =PASSWORD('$pass')");
            $counter = mysqli_num_rows($query);

            if ($counter == 0){
                echo "fail";
            }
            else
            {
                session_start();
                $_SESSION['username'] = $user;

                echo "success";
            }

        }

    }