Masked Card Number (PAN Masking) Regex for PHP

What this pattern does

This page provides a well-structured, multi-part regular expression for matching masked card number (pan masking), ported and verified for PHP. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// Masked Card Number (PAN Masking)
// ReDoS-safe | RegexVault — Finance > Card Numbers

define('MASKED_CARD_NUMBER_PAN_MASKING_PATTERN', '/^[X*]{12}[0-9]{4}$|^[X*]{8}[0-9]{4}$|^[X*]{11}[0-9]{4}$/');

function validate_masked_card_number_pan_masking(string $input): bool {
    return (bool) preg_match(MASKED_CARD_NUMBER_PAN_MASKING_PATTERN, $input);
}

// Example
var_dump(validate_masked_card_number_pan_masking("XXXXXXXXXXXX1234")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Card Numbers category and carries a ReDoS-safe certification. That matters for PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

PCI-DSS allows displaying first 6 and last 4 digits for debugging. This pattern shows only last 4. For display in UI, use: [\*X]{8,12}[0-9]{4} adjusted for 13/15/16-digit cards.