/**
 * 税率计算函数
 *
 * @param 
 * @author 编程之家 jb51.cc jb51.cc
 **/
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);