PHP calculator script

I've been looking all over for 开发者_开发百科a sample script, but I haven't been able to find one. Basically, I want to have the code get a value from a div and multiply that number based on the user input. For example, if I have a site for recipes, and I want to have a calculator where the user enters the amount of servings that they need, and it'll change the recipe to give the amount of servings specified. (you can see an example HERE.)

---

you have to use $_POST or $_GET

To get the users input.

Then you can manipulate it according to your needs and then display it back to the users using echo

---

i think you can solve the problem with Javascript too ! if you are using PHP then do like this

if (isset($_POST['num1'],$_POST['num2'],$_POST['operator']))
{
 ...
}

if you do not use ISSET it will show warnings that $_POST is undefined or so...