Find minimum value in column of 2d array which is not zero

Question

I am using the following code to echo the minimum value in an array:

$array = [
    ['a' =>  0, 'f' => 0, 'l' => 61.60],
    ['a' => 38, 'f' => 0, 'l' => 11.99],
    ['a' => 28, 'f' => 0, 'l' =>  3.40],
];
$min = min(array_column($array, 'a'));
echo $min;

Now I want to exclude 0 from the results, I know I can use array_filter() to achieve this, but do I need to process the array twice?

Answer 1

Yes, this will do:

$min = min(array_filter(array_column($array, 'a')));

It will iterate the array three times, once for each function.

You can use array_reduce to do it in one iteration:

$min = array_reduce($array, function ($min, $val) {
    return $min === null || ($val['a'] && $val['a'] < $min) ? $val['a'] : $min;
});

Whether that's faster or not must be benchmarked, a PHP callback function may after all be slower than three functions in C.

A somewhat more efficient solution without the overhead of a function call would be a good ol' loop:

$min = null;
foreach ($array as $val) {
    if ($min === null || ($val['a'] && $val['a'] < $min)) {
        $min = $val['a'];
    }
}

In the end you need to benchmark and decide on the correct tradeoff of performance vs. readability. In practice, unless you have positively humongous datasets, the first one-liner will probably do just fine.