How to use a custom theme for error pages?

Question

I am developing an application which uses themes for layouts, and I need to use custom themes for all the error pages too.

Looking at the docs, I see that I can change layout fairly easily by using

$this->layout = 'mylayout';

in the error page itself, but I need to change the theme too. I have tried with

$this->theme = 'mytheme';

but the error page is still using the default theme, so I guess this is not the right way to set it.

What is the correct way to set a theme for error pages?

score 3 · Accepted Answer · answered Aug 12 '16 at 16:45

Themes are easiest to be set via the Controller.beforeRender event, or for earlier CakePHP versions, via the Controller::$theme property.

The default exception renderer uses a new controller instance for handling errors, therefore you can for example

Create a custom error controller and add a listener/callback

One option would be to create a custom error controller where you can set the theme as you would in a regular controller. By default CakePHP will use \App\Controller\ErrorController if it exists, so all you'd need to do would be to create the controller.

src/Controller/ErrorController.php

namespace App\Controller;

use Cake\Controller\Controller;
use Cake\Event\Event;

class ErrorController extends Controller
{
    public function beforeRender(Event $event)
    {
        $this->viewBuilder()->theme('ErrorThemeName');
    }
}

Done, all exceptions should now use the ErrorThemeName theme.

Create a custom exception renderer and add a listener to the controller

You could also create a custom/extended exception renderer, and override ExceptionRenderer::_getController(), and add a proper listener for the Controller.beforeRender where you can set the theme.

src/Error/AppExceptionRenderer.php

namespace App\Error;

use Cake\Error\ExceptionRenderer;
use Cake\Event\Event;

class AppExceptionRenderer extends ExceptionRenderer
{
    protected function _getController()
    {
        $controller = parent::_getController();
        $controller->eventManager()->on('Controller.beforeRender', function (Event $event) {
            $event->subject()->viewBuilder()->theme('ErrorThemeName');
        });
        return $controller;
    }
}

config/app.php

// ...
'Error' => [
    'exceptionRenderer' => '\App\Error\AppExceptionRenderer',
    // ...
],
// ...

How to use a custom theme for error pages?

1 Answers1

Create a custom error controller and add a listener/callback

Create a custom exception renderer and add a listener to the controller