American Express Card Number Regex for PHP

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching american express card number, 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
// American Express Card Number
// ReDoS-safe | RegexVault — Finance > Card Numbers

define('AMERICAN_EXPRESS_CARD_NUMBER_PATTERN', '/^3[47][0-9]{13}$/');

function validate_american_express_card_number(string $input): bool {
    return (bool) preg_match(AMERICAN_EXPRESS_CARD_NUMBER_PATTERN, $input);
}

// Example
var_dump(validate_american_express_card_number("378282246310005")); // 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

Amex uses 15-digit card numbers (unlike 16-digit Visa/Mastercard). CVV is 4 digits on the front (not 3 on the back). Amex uses different group format for display: 4-6-5.