codice:
$query_a = mysql_query ("select count(cognome) AS totale from test.identity where username = '$username' and password ='$password' ") or die(mysql_error());
$st=mysql_fetch_assoc($query_a);
if ($st['totale'] == 0)
	echo "Utente sconosciuto";
else
	echo "Autentificato";