$used=array();
$q=mysqli_query("SELECT * FROM inventory WHERE inv_userid=$userid");
while ( $r=mysqli_fetch_array($q) ) {
if ( ! in_array ( $r['inv_id'], $used ) )
{
$currdel=array();
$used[] =$r['inv_id'];
$currdel[]=$r['inv_id'];
$amount=$r['inv_qty'];
$q2=mysqli_query("SELECT * FROM inventory WHERE inv_userid=$userid AND inv_itemid = {$r['inv_itemid']} AND inv_id != {$r['inv_id']}");
while ( $r2 = mysqli_fetch_array($q2) ) {
$used[]=$r2['inv_id'];
$currdel[]=$r2['inv_id'];
$amount+=$r2['inv_qty'];
}
mysqli_query("DELETE FROM inventory WHERE inv_id IN(".implode(",",$currdel).")");
mysqli_query("INSERT INTO inventory VALUES('', {$r['inv_itemid']}, $userid, $amount)");
}
}