sommare due valori array se uguali

[dottwatson]

$query_str="SELECT SUM(quantita) AS totali,
                            dal_data AS from,
                            al_data AS to 
                 FROM    tabella 
                 WHERE  dal_data >= $from_data
                 AND      al_data <= $to_data
                 GROUP BY dal_data
                 ORDER BY dal_data";

$query=mysql_query($query_str);

echo "<pre>";
while ($res=mysql_fetch_assoc($query)) print_r($res);
echo "</pre>"; 

riprova così.. mi sono sbagliato con le date