Create Reusable Validation Rules with the ValidationRule Interface

Generate custom, reusable validation rule objects using php artisan make:rule with the Illuminate\Contracts\Validation\ValidationRule interface.

When complex validation logic (such as validating tax IDs, verifying phone carrier formats, or checking credit card checksums) is needed across multiple Form Requests, writing custom closures or regexes leads to duplicate code.

Laravel provides the ValidationRule contract for custom rule classes.

Generating a Custom Rule

php artisan make:rule Uppercase

Implementing the Rule Class

namespace App\Rules;

use Closure;
use Illuminate\Contracts\Validation\ValidationRule;

class Uppercase implements ValidationRule
{
    public function validate(string $attribute, mixed $value, Closure $fail): void
    {
        if (strtoupper($value) !== $value) {
            $fail("The :attribute must be completely uppercase.");
        }
    }
}

Using the Rule in Form Requests

use App\Rules\Uppercase;

public function rules(): array
{
    return [
        'promo_code' => ['required', 'string', new Uppercase()],
    ];
}

Summary

• Uses the modern single-method validate($attribute, $value, $fail) interface.
• Invoke $fail('message') to record validation failures.
• Highly testable and reusable across Form Requests and Validator instances.