invoiceninja/app/Ninja/Transformers/ContactTransformer.php

<?php namespace App\Ninja\Transformers;

use App\Models\Contact;
use League\Fractal;
use League\Fractal\TransformerAbstract;

class ContactTransformer extends TransformerAbstract
{
    public function transform(Contact $contact)
    {
        return [
            'id' => (int) $contact->public_id,
            'first_name' => $contact->first_name,
            'last_name' => $contact->last_name,
            'email' => $contact->email,
        ];
    }
}