Mask credit card number in PHP

Question

I have credit card number which I want to mask as below:

$cc = 1234123412341234

echo cc_masking($cc)

1234XXXXXXXX1234

function cc_masking($number) {.....}         


        

Answer 1

With regular expression

function cc_masking( $number, $maskChar = 'X' ) {
    return preg_replace(
        '/^(....).*(....)$/',
        '\1' . str_repeat( $maskChar, strlen( $number ) - 8) . '\2',
        $number );
}

You keep the first four characters (and the last four), replacing the others with X.

Answer 2

No need for regular expression for this. Just take n numbers at the beginning, n numbers at the end then add the X in the middle to complete.

Answer 3

If you wish to show only last 4 digits, here is a dynamic way. Works with both credit cards, ACH numbers or anything:

https://gist.github.com/khoipro/815ea292e2e87e10771474dc2ef401ef

    $variable = '123123123';
    $length = strlen($variable);
    $output = substr_replace($variable, str_repeat('X', $length - 4), 0, $length - 4);
    echo $output;

Answer 4

Assuming that:

• Credit card numbers might be contained in a bigger string containing more content
• All major credit cards are sum-checked using the Luhn algorithm https://en.wikipedia.org/wiki/Luhn_algorithm

This is what I do:

• I detect, via regex, if a string contains a chain of digits, separated or not by spaces and hyphens.
• For every match, I strip it from non-numeric values and check if is a valid Luhn.
• Replace the part I want, for every match, with replacement characters (usually "*").

The code is this:

public function mask($string)
{
    $regex = '/(?:\d[ \t-]*?){13,19}/m';

    $matches = [];

    preg_match_all($regex, $string, $matches);

    // No credit card found
    if (!isset($matches[0]) || empty($matches[0]))
    {
        return $string;
    }

    foreach ($matches as $match_group)
    {
        foreach ($match_group as $match)
        {
            $stripped_match = preg_replace('/[^\d]/', '', $match);

            // Is it a valid Luhn one?
            if (false === $this->_util_luhn->isLuhn($stripped_match))
            {
                continue;
            }

            $card_length = strlen($stripped_match);
            $replacement = str_pad('', $card_length - 4, $this->_replacement) . substr($stripped_match, -4);

            // If so, replace the match
            $string = str_replace($match, $replacement, $string);
        }
    }

    return $string;
}

You will see a call to $this->_util_luhn->isLuhn, which is a function that does this:

public function isLuhn($input)
{

    if (!is_numeric($input))
    {
        return false;
    }

    $numeric_string = (string) preg_replace('/\D/', '', $input);

    $sum = 0;

    $numDigits = strlen($numeric_string) - 1;

    $parity = $numDigits % 2;

    for ($i = $numDigits; $i >= 0; $i--)
    {
        $digit = substr($numeric_string, $i, 1);

        if (!$parity == ($i % 2))
        {
            $digit <<= 1;
        }

        $digit = ($digit > 9)
            ? ($digit - 9)
            : $digit;

        $sum += $digit;
    }

    return (0 == ($sum % 10));
}

It is how I implemented it in https://github.com/pachico/magoo/. Hope you find it useful.

Answer 5

$accNum = "1234123412341234";

$accNum1 = substr($accNum,2,2);

$accNum1 = '**'.$accNum1;

$accNum2 = substr($accNum,6,100);

$accNum2 = '**'.$accNum2;

$accNum = $accNum1.$accNum2;

echo $accNum;