I am making a payroll software that calculates the amount the employee should be paid based of certain variables. The variables and rates are loaded from the database in the first script and generates the html input for the person to fill out how much they did. The variables (called vars or units in the script), are just how many that person did. The rate is what they get paid for one of those units. So for each var the total would be unit * the correlating rate. I need to add all the totals of each of these vars to make $subTotal. How do i add the totals in the while loop?
I hope everyone understands my terminology and thanks in advance.

PHP Code:

<?php require("libraries/auth/membersarea.php") ?>
<h2>Work Time</h2>

<?php
$sql = "SELECT * FROM vars  WHERE active = '1' AND adminOnly = '0' ORDER BY ID ASC";

$result = mysql_query($sql);

if (!$result) {
    echo "Could not successfully run query ($sql) from DB: " . mysql_error();
    exit;
}

if (mysql_num_rows($result) == 0) {
    echo "No Published Variables Found!";
    include("template/footer.php");   
    exit;
}
    echo "<form action=\"newpayment_process.php\" method=\"post\">";
while($row = mysql_fetch_array($result))
    {
    echo "<table id=\"line".$row['ID']."\" align=\"center\" border=\"0\" style=\"width: 40%; font-size:14px;\">\r\n<tr>\r\n";
    echo "<td style=\"width: 30%;\"><b>".$row['varName']."</b></td>";
    echo "<td style=\"width: 18%;\"><input type=\"text\" name=\"".$row['ID']."\" /></td>\r\n";
    echo "</tr>\r\n";
    echo "</table>\r\n";
    }
    
?>
<br />
<input type="submit" value="Submit" align="center" />
</form>
<?php include("template/footer.php") ?>

PHP Code:

<?php
// Start Session
session_start();

// Establish Authentication System
require("libraries/auth/membersarea.php");

// Establish Connection to Database
require("libraries/db/dbconnect.php");

//Begin 
    
    $username = $_COOKIE['ID_my_site'];
    $PIDhigh = mysql_result(mysql_query("select max(PID) from payroll"), 0);
    //"Manual" Auto-incrementing of PID 
    $PID = $PIDhigh + 1;
    $userID = mysql_result(mysql_query("select ID from users where username = '$username'"), 0);
    $user_Name = mysql_result(mysql_query("select name from users where username = '$username'"), 0);
    
    mysql_query("insert into payroll (PID, ID, username) 
    values ('".$PID."', '$userID', '$username')") or die(mysql_error());


$sql = "SELECT * FROM vars  WHERE active = '1' AND adminOnly = '0' ORDER BY ID DESC";

$result = mysql_query($sql);

if (!$result) {
    echo "Could not successfully run query ($sql) from DB: " . mysql_error();
    exit;
}

if (mysql_num_rows($result) == 0) {
    echo "No Published Variables Found!";
    include("template/footer.php");   
    exit;
}

    
while($row = mysql_fetch_array($result))
    {
    //ID from vars
    $id = $row['ID'];
    
    //ID's value
    $value = $_POST[$id];
    
    //Generate field names for payroll table
    $field = mysql_result(mysql_query("select varAlias from vars where ID = '".$id."'"), 0);
    $fieldRateText = $field . "_rate";
    
    //Get rates
    $fieldRate = mysql_result(mysql_query("select rate from current_rates where vID = '".$id."'"), 0);
    
    //Dump into MySQL
    mysql_query("update payroll set ".$field." = '".$value."' where PID = '".$PID."'") or die(mysql_error());
    mysql_query("update payroll set ".$fieldRateText." = '".$fieldRate."' where PID = '".$PID."'") or die(mysql_error());
    

    //$varTotal is the total for that var
    $varTotal = $value * $fieldRate;
    
    //$subTotal is the total before taxes
    //Generate $subTotal somehow?
    //$total is the total after taxes

    }

// To be implemented
//Email to administrators that payroll request has been filed
    $adminEmail = mysql_result(mysql_query("select email from users where siteNotify = '1'"), 0);
    $adminName = mysql_result(mysql_query("select name from users where siteNotify = '1'"), 0);
    $emailMessage = "Hello ".$adminName.",\n A payroll request has been submitted by ".$user_Name." and is pending your approval.";
    $emailSubject = "RAI Payroll System - Pending Payroll Submission";
    $emailFrom = "noreply@djabnetworks.com";
    $emailHeader = "From: " . $emailFrom;
    mail($adminEmail,$emailSubject,$emailMessage,$emailHeader);


//Success message
    echo "Your payroll request has been submitted. ".$adminName." has been notified and will confirm your request before it is available on your payroll.";






//End

// Include footer
include("template/footer.php");

?>

Imagine your database looks like this:

id | price | rate

1 | 5 | 2
2 | 3 | 3

With the following code you can get the subtotal:

PHP Code:

$query = mysql_query(" SELECT * FROM test_table ");
while ($row = mysql_fetch_array($query)) {
    $total = $row['price'] * $row['rate'];
    $subtotal += $total; // will output 19
}

echo $subtotal; 


Basially all you will be doing is creating a variable called $subtotal and with each iteration of the while loop you will be adding to (and not replacing) the previous set value:

+=

I believe it would be a whole lot more easily if you draw a program structure first. And I do understand that the thing I am saying now might be too basic, and it might be useless or so, but sometimes we could simplify the matter by breaking it down first. You should state down the entire module that you could use in connecting each other together and which should be solved first, combined together, etc.