Code to Validate Check Digits of JAN Codes in PHP
2023-04-01 11:27 (2 years ago)
ytyng
/**
* Validate the JAN check digit and return [success?, message]
*/
function validate_jan($jan): array
{
$match = preg_match('|^(\d{12})(\d)$|', $jan, $matches);
if (!$match) {
return [false, 'Digit count error'];
}
$chars = str_split($matches[1]);
$odd_total = 0;
$even_total = 0;
foreach ($chars as $i => $v) {
if ($i % 2 == 0) {
// Starting from 0, so 0 is an odd digit
$odd_total += $v;
} else {
$even_total += $v;
}
}
$total = $even_total * 3 + $odd_total;
$digit = (10 - ($total % 10)) % 10;
if ($matches[2] != $digit) {
return [false, "Check digit mismatch. The correct digit is {$digit}"];
}
return [true, ""];
}
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