/**

 * @param $num1

 * @param $num2

 * @param $opt

 * @return float|int

 */

function calc($num1, $num2, $opt)

{

    switch ($opt) {

        case '+':

            $res = $num1 + $num2;

            break;

        case '-':

            $res = $num1 - $num2;

            break;

        case '*':

            $res = $num1 * $num2;

            break;

        case '/':

            if ($num2 != ) {

                $res = $num1 / $num2;

            } else {

                exit('除数不能为0');

            }

            break;

        case '%':

            $res = $num1 % $num2;

            break;

    }

    return $res;

}

echo "\n";

echo calc(, , '+');

echo "\n";

echo calc(, , '/');

echo "\n";

echo calc(, , '%');