Question 46204 in PHP Question posted in
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How to check the highest condition by comparing data from one array to another? – PHP

I would like to apply discounts according to a given rule:

  • If the quantity is greater than 10, apply a 5% discount
  • If the quantity is greater than 20, apply a 10% discount
  • If the quantity is greater than 30, apply a 15% discount

I have expressed said rule in one array.

But I don’t know how to verify that only the highest possible condition is met.

For example, if the amount is greater than 30, apply only 15%.

Any idea how to solve this or improve the logic?

Code

$rules=array(10=>5, 20=>10, 30=>15);
$qty=array(
    array('qty'=>1, 'price'=>100),
    array('qty'=>2, 'price'=>9),
    array('qty'=>10, 'price'=>54),
    array('qty'=>13, 'price'=>22),
    array('qty'=>21, 'price'=>8),
    array('qty'=>22, 'price'=>999),
    array('qty'=>35, 'price'=>2),
    array('qty'=>50, 'price'=>1),
    
);

print("qtytpricetfinalPricen");

foreach ($qty as $item) {
    $finalPrice=$item['price'];
    $discount="";

    foreach ($rules as $k=>$v) {
        if($item['qty'] >= $k) {
            $finalPrice= $finalPrice - ($finalPrice * ($v / 100));
            $discount.="*";
        }
    }    
    printf("%st%st%s%sn",$item['qty'],$item['price'],$finalPrice,$discount);
}

OutPut:

  qty   price   finalPrice
  1     100     100
  2     9       9
  10    54      51.3*
  13    22      20.9*
  21    8       6.84**
  22    999     854.145**
  35    2       1.4535***
  50    1       0.72675***
Tags:

2

Answers


  1. 0

    You could sort the $rules array from the highest key to lowest. This means if we encounter a threshold, we don’t need to do anymore iterations for the lower rule:

    uksort($rules, fn($a, $b) => $b - $a);

    You could rework the calculation statement slightly to be more lean, though this is more stylistic tweak:

    $finalPrice *= (1 - ($v / 100));

    For the discount string, I assumed that an asterisk corresponds to a multiple of 10 corresponding to the discount applied:

    $discount = str_repeat('*', round($k / 10));

    Lastly, we break inside the if since we do not need to process anymore rules for the current item. The saves some iteration cycles.

    Putting it all together:

    uksort($rules, fn($a, $b) => $b - $a);

print("qtytpricetfinalPricen");

foreach ($qty as $item) {
    $finalPrice=$item['price'];
    $discount="";

    foreach ($rules as $k=>$v) {
        if($item['qty'] >= $k) {
            $finalPrice= $finalPrice * (1 - ($v / 100));
            $discount = str_repeat('*', round($k / 10));
            break;
        }
    }
    printf("%st%st%s%sn",$item['qty'],$item['price'],$finalPrice,$discount);
}

    Would output:

    qty price   finalPrice
1   100 100
2   9   9
10  54  51.3*
13  22  20.9*
21  8   7.2**
22  999 899.1**
35  2   1.7***
50  1   0.85***
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  2. 0

    You’re close. Two things are missing:

    Since you test with

    if ($item['qty'] >= $k) {

    you need to sort the $rules array in descending order by its keys, like this:

    $rules = [ 10 => 5, 20 => 10, 30 => 15 ];
krsort($rules);

    The second step is to add a break statement to the inner loop:

    foreach ($rules as $k => $v) {
  if ($item['qty'] >= $k) {
    $finalPrice -= ( $finalPrice * ( $v / 100 ) );
    // $discount .= '*';   
    break;   // Discount found, so stop testing for other discounts
  }
}

    Now the output will be:

    1   100 100
2   9   9
10  54  51.3
13  22  20.9
21  8   7.2
22  999 899.1
35  2   1.7
50  1   0.85

    The line

     $discount .= '*';

    is commented out because it does not make sense anymore. It showed how often a discount was applied. If the purpose is to show the size of the discount – 5 prints: *, 10 prints: **, 15 prints: *** –, then this line would produce that output:

     $discount = str_repeat('*', $v / 5);
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