validar_cartao.php

<?

function validar_cartao($c) {
	$c = ereg_replace("[^0-9]", "", $c);
	$s = 0;
	$v = '';
	$n = strlen($c);
	if ($n != 16) return false;
	if ($c[0] != '4') return false;
	for($i = 0; $i < $n; $i += 2){
		$s = $c[$i]*2;
		if ($s > 9) {
			$s = substr($s, 0, 1) + substr($s, 1, 1);
	    }
		$v .= "$s" . $c[$i+1];
	}
	$s = 0;
	for($i = 0; $i < $n; $i++){
		$s += $v[$i];
	}
	if ($s > 150) return false;
	if ($s % 10 > 0) return false;
	return true;
}

// NÚMEROS CARTÕES PARA TESTE

$cartoes = array();
$cartoes["amex"] = "376411112222331";
$cartoes["mastercard"] = "5555666677778884";
$cartoes["diners"] = "30111122223331";
$cartoes["visa"] = "4073020000000002";
$cartoes["visa2"] = "4111111111111111";
$cartoes["visa3"] = "4012888888881881";
$cartoes["visa4"] = "4222222222222";
$cartoes["hipercard"] = "3841001111222233334";
$cartoes["aura"] = "5078601870000127985";
$cartoes["aura2"] = "5078601800003247449";
$cartoes["American Express"] = "378282246310005";
$cartoes["American Express2"] = "371449635398431";
$cartoes["American Express Corporate"] = "378734493671000";
$cartoes["Australian BankCard"] = "5610591081018250";
$cartoes["Diners Club"] = "30569309025904";
$cartoes["Diners Club2"] = "38520000023237";
$cartoes["Discover"] = "6011111111111117";
$cartoes["Discover2"] = "6011000990139424";
$cartoes["JCB"] = "3530111333300000";
$cartoes["JCB2"] = "3566002020360505";
$cartoes["MasterCard"] = "5555555555554444";
$cartoes["MasterCard2"] = "5105105105105100";

// TESTA E EXIBE OS QUE FALHARAM

foreach($cartoes as $bandeira => $numero):
	if (!validar_cartao($numero))
		echo "$bandeira: $numero\n";
endforeach;

?>