Laravel 5 general error as json

I came here earlier searching for how to throw json exceptions anywhere in Laravel and the answer set me on the correct path. For anyone that finds this searching for a similar solution, here's how I implemented app-wide:

Add this code to the render method of app/Exceptions/Handler.php

if ($request->ajax() || $request->wantsJson()) {
    return new JsonResponse($e->getMessage(), 422);
}

Add this to the method to handle objects:

if ($request->ajax() || $request->wantsJson()) {

    $message = $e->getMessage();
    if (is_object($message)) { $message = $message->toArray(); }

    return new JsonResponse($message, 422);
}

And then use this generic bit of code anywhere you want:

throw new \Exception("Custom error message", 422);

And it will convert all errors thrown after an ajax request to Json exceptions ready to be used any which way you want :-)

Laravel 5.1

To keep my HTTP status code on unexpected exceptions, like 404, 500 403...

This is what I use (app/Exceptions/Handler.php):

 public function render($request, Exception $e)
{
    $error = $this->convertExceptionToResponse($e);
    $response = [];
    if($error->getStatusCode() == 500) {
        $response['error'] = $e->getMessage();
        if(Config::get('app.debug')) {
            $response['trace'] = $e->getTraceAsString();
            $response['code'] = $e->getCode();
        }
    }
    return response()->json($response, $error->getStatusCode());
}

Laravel 5 offers an Exception Handler in app/Exceptions/Handler.php. The render method can be used to render specific exceptions differently, i.e.

public function render($request, Exception $e)
{
    if ($e instanceof API\APIError)
        return \Response::json(['code' => '...', 'msg' => '...']);
    return parent::render($request, $e);
}

Personally, I use App\Exceptions\API\APIError as a general exception to throw when I want to return an API error. Instead, you could just check if the request is AJAX (if ($request->ajax())) but I think explicitly setting an API exception seems cleaner because you can extend the APIError class and add whatever functions you need.