<?php
// check card number
if (!isset($_POST['card_number']) || empty($_POST['card_number'])) {
print 'Please fill card number field';
exit;
} elseif (!preg_match('/^\\d{16}$/', $_POST['card_number'])) {
print 'Card number must contain 16 digits';
exit;
} else {
$card_number = (int) $_POST['card_number'];
if (!is_valid_credit_card($card_number)) {
print 'Incorrect card number';
exit;
}
}
// check month field
if (!isset($_POST['month']) || empty($_POST['month'])) {
print 'Please fill month field';
exit;
} elseif (!preg_match('/^(0[1-9]|1[0-2])$/', $_POST['month'])) {
print 'Incorrect month';
exit;
} else {
$month = $_POST['month'];
}
// check year field
if (!isset($_POST['year']) || empty($_POST['year'])) {
print 'Please fill year field';
exit;
} elseif (!preg_match('/^(1[7-9]|2[0-5])$/', $_POST['year'])) {
<?php
function is_valid_credit_card($s)
{
// Remove non-digits and reverse
$s = strrev(preg_replace('/[^\\d]/', '', $s));
// compute checksum
$sum = 0;
for ($i = 0, $j = strlen($s); $i < $j; $i++) {
// Use even digits as-is
if ($i % 2 == 0) {
$val = $s[$i];
} else {
// Double odd digits and subtract 9 if greater than 9
$val = $s[$i] * 2;
if ($val > 9) {
$val -= 9;
}
}
$sum += $val;
}
// Number is valid if sum is a multiple of ten
return $sum % 10 == 0;
}
if (!is_valid_credit_card($_POST['credit_card'])) {
print 'Sorry, that card number is invalid.';
}
