Credit Card Validation - James Laferriere

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	Credit Card Validation Script

	Credit Card Validation
	A PHP function for validating a credit card number. Works for Visa, Mastercard, American Express and Discover. The function returns a 4-element array: Credit Card type: Visa \|\| Mastercard \|\| American Express \|\| Discover \|\| Unknown Numeric: Card number is all digits: True \|\| False Valid Length: Card number has correct number of digits for the type: True \|\| False Message: Result of the function: {Error Message} \|\| OK Pass a credit card number into the function to get the informational array: $cardinfo = cardtype($cardnum); function cardtype($cardnum) { $cardinfo = array("type" => "Unknown", "numeric" => false, "validlength" => false, "msg" => "OK"); if (substr($cardnum, 0, 2) == "51" or substr($cardnum, 0, 2) == "55") { $cardinfo["type"] = "Mastercard"; } elseif (substr($cardnum, 0, 1) == "4") { $cardinfo["type"] = "Visa"; } elseif (substr($cardnum, 0, 2) == "34" or substr($cardnum, 0, 2) == "37") { $cardinfo["type"] = "American Express"; } elseif (substr($cardnum, 0, 4) == "6011") { $cardinfo["type"] = "Discover"; } $cardinfo["numeric"] = ctype_digit($cardnum); $len = strlen($cardnum); if ($cardinfo["type"] == "Mastercard" and $len == 16) { $cardinfo["validlength"] = true; } elseif ($cardinfo["type"] == "Visa" and ($len == 13 or $len == 16)) { $cardinfo["validlength"] = true; } elseif ($cardinfo["type"] == "American Express" and $len == 15) { $cardinfo["validlength"] = true; } elseif ($cardinfo["type"] == "Discover" and $len == 16) { $cardinfo["validlength"] = true; } if ($cardinfo["type"] == "Unknown") { $cardinfo["msg"] = "Unknown credit card number"; } else { if (!$cardinfo["numeric"]) { $cardinfo["msg"] = "Enter digits only. Do not enter dashes or spaces"; } else { if (!$cardinfo["validlength"]) { $cardinfo["msg"] = "The number you entered appears to be [" . $cardinfo["type"] . "], but the number is not valid"; } } } return $cardinfo; }

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