invoiceninja/app/Ninja/Transformers/UserTransformer.php

<?php namespace App\Ninja\Transformers;

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

class UserTransformer extends TransformerAbstract
{
    public function transform(User $user)
    {
        return [
            'id' => (int) ($user->public_id + 1),
            'first_name' => $user->first_name,
            'last_name' => $user->last_name,
            'email' => $user->email,
        ];
    }
}