RE: need a quick help with an order total module

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http://forums.oscommerce.com/viewtopic.php?p=162951#162951
----------------------------------------------------------------

Joshua,

These are obviously just code snippets but should help.

First there is a little function to find the tax rate for the current tax group.
You can put this function into general.php

[code]////
// Get tax rate from tax description
  function tep_get_tax_rate_from_desc($tax_desc) {
    $tax_query = tep_db_query("select tax_rate from " . TABLE_TAX_RATES . " where tax_description = '" . $tax_desc . "'");
    $tax = tep_db_fetch_array($tax_query);
    return $tax['tax_rate'];
  }
[/code]

The first snippet calculates a percentage discounts effect on tax.
given that the percentage is in $p_deduct

[code]          $tod_amount=0;
          reset($order->info['tax_groups']);
          while (list($key, $value) = each($order->info['tax_groups'])) {
            $god_amout=0;
            $tax_rate = tep_get_tax_rate_from_desc($key);
            $net = $tax_rate * $order->info['tax_groups'][$key];
            if ($net>0) {
              $god_amount = $order->info['tax_groups'][$key] * $p_deduct/100;
              $tod_amount += $god_amount;
              $order->info['tax_groups'][$key] = $order->info['tax_groups'][$key] - $god_amount;
            }
          }           
          $order->info['tax'] -= $tod_amount;
          $order->info['total'] -= $tod_amount; 
[/code]

The second re-calculates tax for a fixed deduction in $f_deduct

[code]          $tod_amount = 0;
          reset($order->info['tax_groups']);
          while (list($key, $value) = each($order->info['tax_groups'])) {
            $tax_rate = tep_get_tax_rate_from_desc($key);
            $net = $tax_rate * $order->info['tax_groups'][$key];
            if ($net>0) {
              $ratio1 = $f_deduct/$net;
              $god_amount = $order->info['tax_groups'][$key] * $ratio1;
              $tod_amount += $god_amount;
              $order->info['tax_groups'][$key] = $order->info['tax_groups'][$key] - $god_amount;
            }
          }           
          $order->info['tax'] -= $tod_amount;
          $order->info['total'] -= $tod_amount;
[/code]

HTH