php实现的简单美国商品税计算函数

<?php 
function tax($total,$tax_amount){ 
  $tax_rate = $tax_amount * .01; 
  $tax = $total * $tax_rate; 
  return $value = $tax + $total; 
} 
$price = 50.00; //In U.S. Dollars 
$taxrate = 6.5; //In percentage 
echo "$".tax($price,$taxrate); 
?>