Cannot access empty proprety

[lorenzos]

L'errore è Fatal error: Cannot access empty property in C:\Programmi\Apache Software Foundation\Apache2.2\htdocs\gestionale\login.php on line 5

<?php
if($_POST["user"] != "" and $_POST["password"] != ""){
require_once("classi/classe.amministratori.php");
$controlla = new Amministratori;
$oggcontr = $controlla->$this->user=$_POST["user"];
$oggcontr = $controlla->$this->password=md5($_POST["password"]);
$oggcontr = $controlla->login();
}

Perchè?