Whethere you are building a shopping cart or just requesting your customer’s credit card number for some purpose, we are constantly faced with abusers that fill invalid or fake credit card numbers. This little function courtesy of SoftwareProjects.com will help you avoid that.

function validCC($cc_num) { $pattern = "/^3[47]d{13}$/";//American Express if (preg_match($pattern,$cc_num)) { return true; }

$pattern = "/^([30|36|38]{2})([0-9]{12})$/";//Diner's Club if (preg_match($pattern,$cc_num)) { return true; }

$pattern = "/^6011d{12}$/";//Discover Card if (preg_match($pattern,$cc_num)) { return true; }

$pattern = "/^5[12345]d{14}$/";//Mastercard if (preg_match($pattern,$cc_num)) { return true; }

$pattern = "/^4d{12}(ddd){0,1}$/";//Visa if (preg_match($pattern,$cc_num)) { return true; }

$pattern = "/^30[012345]d{11}$/";//Diners if (preg_match($pattern,$cc_num)) { return true; }

$pattern = "/^3[68]d{12}$/";//Diners #2 if (preg_match($pattern,$cc_num)) { return true; }

// Not valid return false;
}

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Usage is as follows:

echo validCC("card_number_here");

Of course, it can’t check if the credit card really exists and if it has any ballance, because that’s confidential information, but at least you won’t get random numbers anymore.