# How to Validate Credit Card Numbers Using Laravel‑Validate: ValidCreditCard Rule Explained

> Learn to validate credit card numbers in Laravel using the ValidCreditCard rule. This guide explains the Luhn algorithm implementation for robust credit card validation.

- Repository: [Milwad Khosravi/laravel-validate](https://github.com/milwad-dev/laravel-validate)
- Tags: how-to-guide
- Published: 2026-03-07

---

**Laravel‑Validate ships with a `ValidCreditCard` rule—implemented in [`src/Rules/ValidCreditCard.php`](https://github.com/milwad-dev/laravel-validate/blob/main/src/Rules/ValidCreditCard.php)—that uses the Luhn algorithm to verify credit card syntax and can be used via object instantiation or string-based validation when container registration is enabled.**

The `milwad-dev/laravel-validate` package extends Laravel's validation layer with domain-specific rules for common data types. When you need to validate credit card numbers, the package provides the **`ValidCreditCard`** rule, which performs industry-standard checksum verification without requiring external payment gateways.

## How the ValidCreditCard Rule Works

According to the `milwad-dev/laravel-validate` source code, the `ValidCreditCard` class implements the `Illuminate\Contracts\Validation\Rule` contract and validates numbers using the **Luhn algorithm** (modulus 10).

### Input Normalization

The `passes` method first sanitizes user input to handle real-world formatting variations. It strips all non-digit characters using `preg_replace('/\D/', '', $value)` (lines 14-15 of [`ValidCreditCard.php`](https://github.com/milwad-dev/laravel-validate/blob/main/ValidCreditCard.php)), ensuring that spaces, dashes, or other separators do not invalidate legitimate card numbers like `4111-1111-1111-1111`.

### Luhn Algorithm Verification

After normalization, the rule validates the checksum by reversing the cleaned string and processing each digit. Every second digit from the right is doubled; if the result exceeds 9, the algorithm subtracts 9. The implementation sums all digits and confirms the total is divisible by 10 (`$sum % 10 == 0`) according to lines 20-31 of [`src/Rules/ValidCreditCard.php`](https://github.com/milwad-dev/laravel-validate/blob/main/src/Rules/ValidCreditCard.php). This detects most accidental transcription errors and invalid number sequences.

## Implementing Credit Card Validation

You can apply the validator using two syntax patterns depending on your service provider configuration.

### Object Instantiation Syntax

The most explicit method instantiates the rule directly. This approach is always available regardless of configuration settings:

```php
use Milwad\LaravelValidate\Rules\ValidCreditCard;

return [
    'credit_card' => ['required', new ValidCreditCard()],
];

```

### Container-Based String Syntax

When you set `using_container` to `true` in the package configuration, the `LaravelValidateServiceProvider` (lines 75-88) registers the rule in Laravel's service container. This enables the shorter string syntax:

```php
return [
    'credit_card' => 'required|ValidCreditCard',
];

```

The package documentation in [`docs/1.x/valid-credit-card.md`](https://github.com/milwad-dev/laravel-validate/blob/main/docs/1.x/valid-credit-card.md) demonstrates validation using the test number `4111111111111111`, which you can use in development to verify your implementation.

## Customizing Error Messages

When validation fails, the rule returns a translatable error message. The `message` method returns `__('validate.credit-card')` (lines 37-40 of [`ValidCreditCard.php`](https://github.com/milwad-dev/laravel-validate/blob/main/ValidCreditCard.php)). To customize the text, publish the package's language files and override the `credit-card` key in your translation files.

## Summary

- The **`ValidCreditCard`** rule in [`src/Rules/ValidCreditCard.php`](https://github.com/milwad-dev/laravel-validate/blob/main/src/Rules/ValidCreditCard.php) validates credit card syntax using the standard Luhn algorithm.
- Input is automatically normalized by stripping non-digit characters via `preg_replace('/\D/', '', $value)` before checksum calculation.
- You can instantiate the rule directly with `new ValidCreditCard()` or use string syntax when `using_container` is enabled in the service provider registration (lines 75-88).
- Error messages are fully translatable through the `validate.credit-card` language key.

## Frequently Asked Questions

### Does Laravel‑Validate support all credit card types?

The `ValidCreditCard` rule verifies the numeric checksum using the universal Luhn algorithm, which is valid for Visa, MasterCard, American Express, and other major issuers. However, it does not validate specific card type prefixes or lengths; for brand-specific validation, combine this rule with additional custom logic.

### Can users enter credit card numbers with spaces or dashes?

Yes. The rule automatically strips non-digit characters during the normalization phase (lines 14-15 of [`ValidCreditCard.php`](https://github.com/milwad-dev/laravel-validate/blob/main/ValidCreditCard.php)), so formatted numbers like `4111-1111-1111-1111` or `4111 1111 1111 1111` are accepted and validated correctly against the Luhn checksum.

### How do I customize the validation error message?

Publish the package's translation files and modify the `validate.credit-card` key. The rule retrieves the message using `__('validate.credit-card')` (lines 37-40), making it fully customizable per locale without modifying the vendor source code.

### Is the Luhn algorithm implementation secure for production use?

The checksum verification in [`src/Rules/ValidCreditCard.php`](https://github.com/milwad-dev/laravel-validate/blob/main/src/Rules/ValidCreditCard.php) correctly implements the Luhn standard (lines 20-31) and safely detects most accidental input errors. While it validates syntax, always combine this with PCI-compliant payment processing and never log or store raw card data in application databases.