<?php 

$db=$GLOBALS['db'];
$r=$db->query("select * from ecminvoiceouts");
while($a=$db->fetchByAssoc($r)){
   $db->query("update ecminvoiceouts set purchase_price=(select round(sum(quantity*price_purchase),2) as sum from ecminvoiceoutitems 
 where  ecminvoiceout_id='".$a['id']."') where id='".$a['id']."'
           ");
}
?>