Laravel address validation with a custom rule

How do I call the PAF API from a service?

Wrap the HTTP call in a service using Laravel's Http client and a config-based key:

// app/Services/AddressLookup.php
use Illuminate\Support\Facades\Http;

class AddressLookup
{
    public function exists(string $postcode): bool
    {
        $res = Http::withToken(config('services.autopostcode.key'))
            ->get('https://api.autopostcode.com/v1/lookup', ['postcode' => $postcode]);

        return $res->ok() && count($res->json('addresses', [])) > 0;
    }
}

How do I write the custom rule?

Create a rule that delegates to the service so it stays thin and testable:

// app/Rules/ValidUkPostcode.php
use Illuminate\Contracts\Validation\ValidationRule;
use App\Services\AddressLookup;

class ValidUkPostcode implements ValidationRule
{
    public function validate(string $attr, mixed $value, \Closure $fail): void
    {
        if (! app(AddressLookup::class)->exists($value)) {
            $fail('The :attribute is not a recognised UK postcode.');
        }
    }
}

How do I apply it in a Form Request?

Add the rule to your Form Request and Laravel runs it automatically:

// app/Http/Requests/StoreOrderRequest.php
public function rules(): array
{
    return [
        'postcode' => ['required', 'string', new ValidUkPostcode()],
    ];
}

Format check vs PAF validation

For a framework-agnostic PHP example see PHP postcode lookup, power the check with the UK address validation API, and get set up fast with the API quickstart.

A UK-first, affordable alternative

AutoPostcode uses the same Royal Mail PAF data as Loqate, Fetchify and Ideal Postcodes, with a REST API that slots neatly into Laravel's validation pipeline.