UPDATE not working right in while loop

I am trying to get info from a table, add rows in that table, and put the added value back into the table in another field...I want to add field1 and field2 of every row and put the total in the total row.
Heres what the echo gives me

Susan 14

Mary 18

Bob 13

Sam 21

heres the database
mysql> SELECT total_val FROM table;

+-----------+
| total_val |
+-----------+
| 21 |
| 21 |
| 21 |
| 21 |
+-----------+



heres the code....


<?php

require("connection.php");


mysql_select_db("database", $connection);
echo "<br />";

$result = mysql_query("SELECT * FROM table");

while($row = mysql_fetch_array($result))
{

$values = ($row['field1'] + $row['field2']);

echo "values = " . $values;


$sql=mysql_query("UPDATE table SET total = '$values'");


echo $row['user_name'] . " " . $values;
echo "<br />";

}

?>

also note that if I put a INT in place of $values - the echo changes to match...why??

PLEASE help...I have been working on this for 2 entire days....

 

You should specify which row to update in your table like
$sql=mysql_query("UPDATE table SET total = '$values' WHERE user_name='".$row['user_name']."'");
Cause if you don't every record in the table will be updated