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Re: [PHP3] Credit Card
From: Stefan Powell (spowell <email protected>)
Date: 07/30/98
Guoneng Zhong wrote:
>
> Hi,
> Would anyone know the credit card verification algorithm or where it can
> be found? I am writing part of a shopping cart and I want to make sure
> the credit card number is at least valid. Thanks!
You'll need to check the length, the start digits and a LUHN Mod 10
checksum.
Here is a good document that outlines the checks for various cards...
http://www.beachnet.com/~hstiles/cardtype.html
AND (drum roll please...)
------------SNIP!----------------
<?php
//Stefan's slightly obfuscated, but much improved LUHNMod10
function LUHNMod10($ccnum) {
if (!isset($ccnum)) return FALSE;
$sum = 0;
$len = strlen($ccnum);
$ccnum=ereg_replace('[^[:digit:]]+','',$ccnum);
for($idx=0;$idx<$len;$idx++) {
$digit = substr($ccnum,$idx,1);
if ($idx%2) {$sum += ($digit >= 5) ? 1+(($digit*2)%10) : $digit*2;}
else {$sum += $digit;}
}
if ($sum%10) return FALSE;
return TRUE;
}
if (LUHNMod10($ccn)) {
echo "OK! Lets go shoppin!";
}
else {
echo "WhuchutalkinabouWillis?";
}
?>
<form action="<?php echo $SCRIPT_NAME ?>">
<input type="text" name="ccn">
</form>
------------SNIP!----------------
There you go.
BTW, if anyone is having trouble with that algorithm just send me your
credit card number and I'll test it for you. ;-)
--Stef
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