モジュラス10 ウェイト3 の再発明

mod10w3.php

<?php

function mod10w3(string $numeric) {
    $num_array  = array_reverse(str_split($numeric));
    $sum_odd    = array_sum(array_map('current', array_chunk(array_slice($num_array, 0), 2)));
    $sum_even   = array_sum(array_map('current', array_chunk(array_slice($num_array, 1), 2)));
    $sum_all    = ($sum_odd * 3) + $sum_even;
    $mod        = $sum_all % 10;
    $cd         = ($mod == 0) ? 0 : (10 - $mod);
    return $cd;
}

?>