Danack

  1. Customer places an order.
  2. SYN: Can I charge $30?
  3. SYN/ACK: Yes.
  4. ACK + SYN: Do it.
  5. SYN/ACK: I am gonna do it.
  6. ACK: I see that you're gonna do it.
  

    $user = new RegisteredUser();
    // Any code that touches $user here will be bad
    $user->setEmail($email);

    function foo(int $bar){...}

    foo(36/$value);

    function validateOrderAmount($value) : int {
        $count = preg_match("/[^0-9]*/", $value);
        
        if ($count) {
            throw new InvalidOrderAmount("Order amount must contain only digits.");
        }

        $value = intval($value);

        if ($value < 1) {
            throw new InvalidOrderAmount("Order amount must be one or more.");
        }
        
        if ($value >= MAX_ORDER_AMOUNT) {
            throw new InvalidOrderAmount("You can only order ".MAX_ORDER_AMOUNT." at a time.");
        }
        
        return $value;
    }

    function processOrderRequest() {
        $orderAmount = validateOrderAmount($_REQUEST['orderAmount']);
    
        //Yay, our IDE/static code analyzer can tell that $amount is an int if the code reached here.
        placeOrder($orderAmount);
    }