count value in If statement for different condition's result

Question

Each customers who buy 5 products, they will get bonus of 2 products.

However, each customer who buy 10 products, they will get bonus of 6 products.

The problem now is what if there is customer who buy 26 products?

So the condition will be :

the customer buy

 (10 x 2) //get 6 products x 2 = 12 products bonus/free 

   + 

 (5 x 1) // get 2 products x 1 = 2 products bonus/free

So far here is my condition:

if ($quatity > 4 && $quatity < 10){
    echo "Congrats, you get 2 products free"
}

if ($quatity > 9){
    echo "Congrats, you get 6 products free"
}

The code above is working fine with me if only the customer buy more than 5 or 10 products.

But as I mentioned above, what if the customer buy more than 10 products such as 26 products or 200 products? Should I write if function manually such as if ($quatity > 9){} , if ($quatity > 19){} , if ($quatity > 29){} , if ($quatity > 39){} , and so on,

OR

can anybody figure out the simple way for this?

Thanks in advance!

Answer 1

This code will give you what you want.

It will break down the 10 products bonus, and then see if there are any 5 bonus left to give.

$tenBonus = (int)($quatity / 10);
$fiveBonus = $quatity % 10 > 4 ? 1 : 0;
$bonus = ($tenBonus * 5) + ($fiveBonus * 2);
if($bonus > 0) {
    echo "Congrats, you get ". $bonus ." products free";
}