Refactor pcbid generator (clean code reference)

[icex2]

confidential issue because the source asked to not share the snippet in public.

translate the following php code snippet which is based on the implemented from bemanitools (decompiled code) and feed it back to the project. make sure to test the new against the previous implementation (unit test highly adviced).

<?php

class PcbId {

    const HEADER = 0x01;

    public static function generate(?string $id_hex = null): string {

        $id = $id_hex ? hex2bin($id_hex) : random_bytes(8);

        $checksum = self::getChecksum($id);
        return strtoupper(bin2hex(chr(self::HEADER) . $id . chr($checksum)));
    }

    public static function verify(string $input_hex): bool  {

        $input = hex2bin($input_hex);

        $header = substr($input, 0, 1);
        $id = substr($input, 1, 8);
        $checksum = substr($input, -1);

        $expected_checksum = self::getChecksum($id);

        return $header == chr(self::HEADER) && $checksum == chr($expected_checksum);
    }

    private static function getChecksum(string $id): int {

        $checksum = 0;

        $map = [1, 7, 6, 5, 4, 3, 2];

        $length = count($map);

        for($i = 0; $i < $length; $i++) {
            $byte = ord($id[$map[$i]]);
            for($j = 0; $j < 8; $j++) {
                $should_xor = ($checksum ^ ($byte >> $j)) & 1;
                $checksum = $checksum >> 1;
                if($should_xor) $checksum ^= 0x8c;
            }
        }

        return $checksum;
    }

}