Laravel 5.1 Custom Parameter on Custom Exception

I am trying to create a custom exception with a custom parameter in it. I feel like I am doing something wrong here. Basically I would like to handle the exception in Laravel's exception handling file but I need extra data with the exception to know things like who caused the exception. This is what I have so far...

<?php

namespace App\Exceptions;

use Exception;

class ApiException extends \Exception
{
    public $userId;

    public function __construct($userId, $message, $code, Exception $previous)
    {
        parent::__construct($message, $code, $previous);
        $this->userId = $userId;
    }

}

The idea here was to pass the userId into the exception so I can access it later. But I am having a problem. In this case, I don't know what to pass in as the "$previous" variable...

throw new ApiException($user->id, 'im testing', 200, $previous);

Any help would be greatly appreciated.

via Chebli Mohamed