Każda z poniższych funkcji na wejściu przyjmuje numer (w większości przypadków może on zawierać także spacje lub myślniki) a zwraca TRUE lub FALSE w zależności od tego czy numer jest poprawny czy też nie. Żadna filozofia.

PESEL

function check_pesel_number ($number)
{
	$w = array(1, 3, 7, 9, 1, 3, 7, 9, 1, 3);
	if (($l = strlen($number = preg_replace('/[^0-9]/', '', $number))) !== count($w) + 1) return false;
	for ($s = $i = 0; $i < $l - 1; $i ++)
		$s += $number[$i] * $w[$i];
	return $number[$l - 1] == ((10 - ($s % 10)) % 10);
}Code language: PHP (php)

NIP

function check_nip_number ($number)
{
	$w = array(6, 5, 7, 2, 3, 4, 5, 6, 7);
	if (($l = strlen($number = preg_replace('/[^0-9]/', '', $number))) !== count($w) + 1) return false;
	for ($s = $i = 0; $i < $l - 1; $i ++)
		$s += $number[$i] * $w[$i];
	return (10 > ($c = ($s % 11))) && $number[$l - 1] == $c;
}Code language: PHP (php)

REGON

function check_regon_number ($number)
{
	$w = array(7 => array(2, 3, 4, 5, 6, 7), 9 => array(8, 9, 2, 3, 4, 5, 6, 7), 14 => array(2, 4, 8, 5, 0, 9, 7, 3, 6, 1, 2, 4, 8));
	if (!isset($w[$l = strlen($number = preg_replace('/[^0-9]/', '', $number))])) return false;
	for ($s = $i = 0; $i < $l - 1; $i ++)
		$s += $number[$i] * $w[$l][$i];
	return $number[$l - 1] == (($s % 11) % 10);
}Code language: PHP (php)

Dowód Osobisty

function check_do_number ($number)
{
	$t = 0;
	$n = array();
	$w = array(7, 3, 1);
	if (!preg_match('/^([A-Z]+)(\d{1})(\d+)$/', strtoupper($number), $n)) return false;
	foreach (str_split($n[1] . $n[3]) as $i => $l)
		$t += $w[$i % 3] * (is_numeric($l) ? $l : (ord($l) - 55));
	return ($t % 10) == (int)$n[2] ? true : false;
}Code language: PHP (php)

PWZ

(Prawo Wykonywania Zawodu)

function check_pwz_number ($number)
{
	if (strlen($number) != 7 || preg_match('/^0+$/', $number)) return false;
	$c = (int)$number[0];
	$n = substr($number, 1);
	$s = 0;
	for ($i = 1; $i <= 6; $i ++) $s += (int)$n[$i - 1] * $i;
	return ($s % 11) == $c ? true : false;
}Code language: PHP (php)

IBAN

(tylko dla polskich oddziałów banków)

function check_iban_number ($number)
{
	$w = array(7, 1, 3, 9, 7, 1, 3);
	$number = preg_replace('/[^A-Z0-9]/', '', !preg_match('/^([A-Z]{2})/', $number = strtoupper($number)) ? 'PL' . $number : $number);
	if (preg_match('/^PL/', $number))
	{
		for ($s = $i = 0; $i < 7; $i ++)
			$s += $number[4 + $i] * $w[$i];
		if (($s % 10) != (int)$number[11])
			return false;
	}
	$number = substr($number, 4) . substr($number, 0, 4);
	foreach (str_split(substr(preg_replace_callback('/([A-Z])/', function ($match) { return (ord($match[0]) - 55); }, $number), 0, -2) . '00', 6) as $n)
		$r = (int)((isset($r) ? $r : '') . $n) % 97;
	return strcmp(sprintf('%02d', 98 - $r), substr($number, -2)) == 0;
}Code language: PHP (php)

IMEI

function check_imei_number ($number)
{
	$number = preg_replace('/[^0-9]/', '', $number);
	for ($c = 0, $i = 0; $i < strlen($number) - 1; $i ++)
		$c += array_sum(str_split($number[$i] * (($i + 1) % 2 == 0 ? 2 : 1)));
	return (int)$number[strlen($number) - 1] === (10 - ($c % 10));
}Code language: PHP (php)