用php简单实现加减乘除计算器

 <?phpheader("content-type:text/html;charset=utf-8");session_start();?>        
 第一个数
 计算符号 + - * / 
 第二个数
 
 
   <?php$num1 = $_POST['num1'];$num2 = $_POST['num2'];$oper = $_POST['oper'];$rs = 0;switch ($oper) {    case "+":        $rs = $num1 + $num2;        break;    case "-":        $rs = $num1 - $num2;        break;    case "*":        $rs = $num1 * $num2;        break;    case "/":        $rs = $num1 / $num2;        break;    default:        echo "您输入的不正确";}$_SESSION['rs'] = $rs;echo '计算结果为：' . $_SESSION['rs'];?>