计算每个额外项目的运费折扣

Question

I am trying to create a loop in PHP where for each extra item in a shopping cart, the shipping gets a ascending 10% discount.

This is the result I want:

• Quantity = 1: Shipping = 30;
• Quantity = 2: Shipping = 30 + (30 x 0.5);
• Quantity = 3: Shipping = 45 + (30 x 0.4);
• Quantity = 4: Shipping = 57 + (30 x 0.3);
• Quantity = 5: Shipping = 69 + (30 x 0.2);
• Quantity = 6: Shipping = 78 + (30 x 0.1);
• Quantity = 7: Shipping = 81 + (30 x 0.1);
• Quantity = 8: Shipping = 84 + (30 x 0.1);

etc.

I don't know where to place my $quantity variable now.

My PHP:

<?php
$quantity = 10;
$shipping = 30;

for( $discount = 0.5; $discount >= 0.1; $discount - 0.1 ) {

    $shipping = $shipping + ( $shipping * $discount );  

}

echo $shipping;
?>

Answer 1

you should iterate the quantity value, not the discount.

$shippingDefault = 30;
$discount = 0.5;
for ($i = 2 ; $i <= $quantity; $i++) {
    if ($discount < 0.1) { 
        $discount = 0.1;
    }
    $shipping += ( $shippingDefault * $discount );
    $discount -= 0.1; 
}