Question

I am attempting to find the closest product to the given budget

$array = array(
    'productname1' => 5,
    'productname2' => 10,
    'productname3' => 15
)

$budget = 12;

I have tried using a function like the following to find the nearest value, but it only returns the number which is closest to the budget rather than the product name.

   function closest($array, $number) {
        sort($array);
        foreach ($array as $a) {
            if ($a >= $number) return $a;
        }
        return end($array);
    }

I can’t help but think there is a MUCH better implementation of this. Any help would be much appreciated.

Answer 1

foreach($array as $k => $v){ $diff[abs($v - $budget)] = $k; }
ksort($diff, SORT_NUMERIC);
$closest_key = current($diff);

var_dump($closest_key);         // Product Name
var_dump($array[$closest_key]); // Product Cost

Prints:

    string(12) "productname2"
    int(10)

Or as a function:

function closest($array, $price)
{
    foreach($array as $k => $v){ $diff[abs($v - $price)] = $k; }
    ksort($diff, SORT_NUMERIC);
    $closest_key = current($diff);
    return array($closest_key, $array[$closest_key]);
}

print_r(closest($array, $budget));

Prints:

    Array
    (
        [0] => productname2  // Product Name
        [1] => 10            // Product Price
    )

Both formats include only three steps:

• Calculate the difference between the product cost and the budget
• Sort these
• Take the first element from the sorted array (the element whose price is closest to the budget).

EDIT: If you don’t care about anything other than the single closest product, then a sort is overkill and a simple min() function (like Emil used) would be a lot faster. For example:

function closest($array, $price)
{
    foreach($array as $k => $v){ $diff[abs($v - $price)] = $k; }
    $closest_key = $diff[min(array_keys($diff))];
    return array($closest_key, $array[$closest_key]);
}