How to sum mysql values in multple while PHP -

i sum row values $orderfeed_query. when echo $sum, sum last loop.

how can can add sum of following loop on $sum variable? dont know how many loops order have.

$checkorder = mysql_query("select * orders  `email` = '$email' ") or die(mysql_error()); while ($row = mysql_fetch_assoc($checkorder)) {     $orderid = $row["orderid"];     $check_order = $row["check_order"];      if($check_order[0] == 1){          $orderfeed_query = mysql_query("select * orderfeed `orderid` = '$orderid' , `product` = '1'") or die(mysql_error());         while ($row = mysql_fetch_assoc($orderfeed_query)) {             $signaturewiz = $row["signaturewiz"];             $flurstueckwiz = $row["flurstueckwiz"];             $uploadwiz = $row["uploadwiz"];             $exsignaturewiz = $row["exsignaturewiz"];             $ibanwiz = $row["ibanwiz"];              $sum = $signaturewiz+$flurstueckwiz+$uploadwiz+$exsignaturewiz+$ibanwiz;              echo $sum;          }     }     } }    

this code

$sum = $signaturewiz + $flurstueckwiz + $uploadwiz + $exsignaturewiz + $ibanwiz; 

overwrites sum each time. must add sum not overwrite

$sum += $signaturewiz + $flurstueckwiz + $uploadwiz + $exsignaturewiz + $ibanwiz; 

and declare $sum = 0; before main loop