Error & Exception Handling

CakePHP applications come with error and exception handling setup for you. PHP errors are trapped and displayed or logged. Uncaught exceptions are rendered into error pages automatically.

Error & Exception Configuration

Error configuration is done in your application’s config/app.php file. By default CakePHP uses Cake\Error\ErrorHandler to handle both PHP errors and exceptions by default. The error configuration allows you to customize error handling for your application. The following options are supported:

  • errorLevel - int - The level of errors you are interested in capturing. Use the built-in PHP error constants, and bitmasks to select the level of error you are interested in. You can set this to E_ALL ^ E_USER_DEPRECATED to disable deprecation warnings.
  • trace - bool - Include stack traces for errors in log files. Stack traces will be included in the log after each error. This is helpful for finding where/when errors are being raised.
  • exceptionRenderer - string - The class responsible for rendering uncaught exceptions. If you choose a custom class you should place the file for that class in src/Error. This class needs to implement a render() method.
  • log - bool - When true, exceptions + their stack traces will be logged to Cake\Log\Log.
  • skipLog - array - An array of exception classnames that should not be logged. This is useful to remove NotFoundExceptions or other common, but uninteresting log messages.
  • extraFatalErrorMemory - int - Set to the number of megabytes to increase the memory limit by when a fatal error is encountered. This allows breathing room to complete logging or error handling.

By default, PHP errors are displayed when debug is true, and logged when debug is false. The fatal error handler will be called independent of debug level or errorLevel configuration, but the result will be different based on debug level. The default behavior for fatal errors is show a page to internal server error (debug disabled) or a page with the message, file and line (debug enabled).

Note

If you use a custom error handler, the supported options will depend on your handler.

class ExceptionRenderer(Exception $exception)

Changing Exception Handling

Exception handling offers several ways to tailor how exceptions are handled. Each approach gives you different amounts of control over the exception handling process.

  1. Customize the error templates This allows you to change the rendered view templates as you would any other template in your application.
  2. Customize the ErrorController This allows you to control how exception pages are rendered.
  3. Customize the ExceptionRenderer This allows you to control how exception pages and logging are performed.
  4. Create & register your own error handler This gives you complete control over how errors & exceptions are handled, logged and rendered.

Customize Error Templates

The default error handler renders all uncaught exceptions your application raises with the help of Cake\Error\ExceptionRenderer, and your application’s ErrorController.

The error page views are located at src/Template/Error/. By default all 4xx errors use the error400.ctp template, and all 5xx errors use the error500.ctp. Your error templates will have the following variables available:

  • message The exception message.
  • code The exception code.
  • url The request URL.
  • error The exception object.

In debug mode if your error extends Cake\Core\Exception\Exception the data returned by getAttributes() will be exposed as view variables as well.

Note

You will need to set debug to false, to see your error404 and error500 templates. In debug mode, you’ll see CakePHP’s development error page.

Customize the Error Page Layout

By default error templates use src/Template/Layout/error.ctp for a layout. You can use the layout property to pick a different layout:

// inside src/Template/Error/error400.ctp
$this->layout = 'my_error';

The above would use src/Template/Layout/my_error.ctp as the layout for your error pages.

Many exceptions raised by CakePHP will render specific view templates in debug mode. With debug turned off all exceptions raised by CakePHP will use either error400.ctp or error500.ctp based on their status code.

Customize the ErrorController

The App\Controller\ErrorController class is used by CakePHP’s exception rendering to render the error page view and receives all the standard request life-cycle events. By modifying this class you can control which components are used and which templates are rendered.

Change the ExceptionRenderer

If you want to control the entire exception rendering and logging process you can use the Error.exceptionRenderer option in config/app.php to choose a class that will render exception pages. Changing the ExceptionRenderer is useful when you want to provide custom error pages for application specific exception classes.

Your custom exception renderer class should be placed in src/Error. Let’s assume our application uses App\Exception\MissingWidgetException to indicate a missing widget. We could create an exception renderer that renders specific error pages when this error is handled:

// In src/Error/AppExceptionRenderer.php
namespace App\Error;

use Cake\Error\ExceptionRenderer;

class AppExceptionRenderer extends ExceptionRenderer
{
    public function missingWidget($error)
    {
        $response = $this->controller->response;

        return $response->withStringBody('Oops that widget is missing.');
    }
}

// In config/app.php
'Error' => [
    'exceptionRenderer' => 'App\Error\AppExceptionRenderer',
    // ...
],
// ...

The above would handle our MissingWidgetException, and allow us to provide custom display/handling logic for those application exceptions.

Exception rendering methods receive the handled exception as an argument, and should return a Response object. You can also implement methods to add additional logic when handling CakePHP errors:

// In src/Error/AppExceptionRenderer.php
namespace App\Error;

use Cake\Error\ExceptionRenderer;

class AppExceptionRenderer extends ExceptionRenderer
{
    public function notFound($error)
    {
        // Do something with NotFoundException objects.
    }
}

Changing the ErrorController Class

The exception renderer dictates which controller is used for exception rendering. If you want to change which controller is used to render exceptions, override the _getController() method in your exception renderer:

// in src/Error/AppExceptionRenderer
namespace App\Error;

use App\Controller\SuperCustomErrorController;
use Cake\Error\ExceptionRenderer;

class AppExceptionRenderer extends ExceptionRenderer
{
    protected function _getController()
    {
        return new SuperCustomErrorController();
    }
}

// in config/app.php
'Error' => [
    'exceptionRenderer' => 'App\Error\AppExceptionRenderer',
    // ...
],
// ...

Creating your Own Error Handler

By replacing the error handler you can customize the entire error & exception handling process. By extending Cake\Error\BaseErrorHandler you can customize display logic more simply. As an example, we could build a class called AppError to handle our errors:

// In config/bootstrap.php
use App\Error\AppError;

$errorHandler = new AppError();
$errorHandler->register();

// In src/Error/AppError.php
namespace App\Error;

use Cake\Error\BaseErrorHandler;

class AppError extends BaseErrorHandler
{
    public function _displayError($error, $debug)
    {
        echo 'There has been an error!';
    }

    public function _displayException($exception)
    {
        echo 'There has been an exception!';
    }
}

The BaseErrorHandler defines two abstract methods. _displayError() is used when errors are triggered. The _displayException() method is called when there is an uncaught exception.

Changing Fatal Error Behavior

Error handlers convert fatal errors into exceptions and re-use the exception handling logic to render an error page. If you do not want to show the standard error page, you can override it:

// In src/Error/AppError.php
namespace App\Error;

use Cake\Error\BaseErrorHandler;

class AppError extends BaseErrorHandler
{
    // Other methods.

    public function handleFatalError($code, $description, $file, $line)
    {
        return 'A fatal error has happened';
    }
}

Creating your own Application Exceptions

You can create your own application exceptions using any of the built in SPL exceptions, Exception itself, or Cake\Core\Exception\Exception. If your application contained the following exception:

use Cake\Core\Exception\Exception;

class MissingWidgetException extends Exception
{
}

You could provide nice development errors, by creating src/Template/Error/missing_widget.ctp. When in production mode, the above error would be treated as a 500 error and use the error500 template.

If your exceptions have a code between 400 and 506 the exception code will be used as the HTTP response code.

The constructor for Cake\Core\Exception\Exception allows you to pass in additional data. This additional data is interpolated into the the _messageTemplate. This allows you to create data rich exceptions, that provide more context around your errors:

use Cake\Core\Exception\Exception;

class MissingWidgetException extends Exception
{
    // Context data is interpolated into this format string.
    protected $_messageTemplate = 'Seems that %s is missing.';

    // You can set a default exception code as well.
    protected $_defaultCode = 404;
}

throw new MissingWidgetException(['widget' => 'Pointy']);

When rendered, this your view template would have a $widget variable set. If you cast the exception as a string or use its getMessage() method you will get Seems that Pointy is missing..

Logging Exceptions

Using the built-in exception handling, you can log all the exceptions that are dealt with by ErrorHandler by setting the log option to true in your config/app.php. Enabling this will log every exception to Cake\Log\Log and the configured loggers.

Note

If you are using a custom exception handler this setting will have no effect. Unless you reference it inside your implementation.

Built in Exceptions for CakePHP

HTTP Exceptions

There are several built-in exceptions inside CakePHP, outside of the internal framework exceptions, there are several exceptions for HTTP methods

exception Cake\Http\Exception\BadRequestException

Used for doing 400 Bad Request error.

exception Cake\Http\Exception\UnauthorizedException

Used for doing a 401 Unauthorized error.

exception Cake\Http\Exception\ForbiddenException

Used for doing a 403 Forbidden error.

New in version 3.1: InvalidCsrfTokenException has been added.

exception Cake\Http\Exception\InvalidCsrfTokenException

Used for doing a 403 error caused by an invalid CSRF token.

exception Cake\Http\Exception\NotFoundException

Used for doing a 404 Not found error.

exception Cake\Http\Exception\MethodNotAllowedException

Used for doing a 405 Method Not Allowed error.

exception Cake\Http\Exception\NotAcceptableException

Used for doing a 406 Not Acceptable error.

New in version 3.1.7: NotAcceptableException has been added.

exception Cake\Http\Exception\ConflictException

Used for doing a 409 Conflict error.

New in version 3.1.7: ConflictException has been added.

exception Cake\Http\Exception\GoneException

Used for doing a 410 Gone error.

New in version 3.1.7: GoneException has been added.

For more details on HTTP 4xx error status codes see RFC 2616#section-10.4.

exception Cake\Http\Exception\InternalErrorException

Used for doing a 500 Internal Server Error.

exception Cake\Http\Exception\NotImplementedException

Used for doing a 501 Not Implemented Errors.

exception Cake\Http\Exception\ServiceUnavailableException

Used for doing a 503 Service Unavailable error.

New in version 3.1.7: Service Unavailable has been added.

For more details on HTTP 5xx error status codes see RFC 2616#section-10.5.

You can throw these exceptions from your controllers to indicate failure states, or HTTP errors. An example use of the HTTP exceptions could be rendering 404 pages for items that have not been found:

// Prior to 3.6 use Cake\Network\Exception\NotFoundException
use Cake\Http\Exception\NotFoundException;

public function view($id = null)
{
    $article = $this->Articles->findById($id)->first();
    if (empty($article)) {
        throw new NotFoundException(__('Article not found'));
    }
    $this->set('article', $article);
    $this->set('_serialize', ['article']);
}

By using exceptions for HTTP errors, you can keep your code both clean, and give RESTful responses to client applications and users.

Using HTTP Exceptions in your Controllers

You can throw any of the HTTP related exceptions from your controller actions to indicate failure states. For example:

use Cake\Network\Exception\NotFoundException;

public function view($id = null)
{
    $article = $this->Articles->findById($id)->first();
    if (empty($article)) {
        throw new NotFoundException(__('Article not found'));
    }
    $this->set('article', 'article');
    $this->set('_serialize', ['article']);
}

The above would cause the configured exception handler to catch and process the NotFoundException. By default this will create an error page, and log the exception.

Other Built In Exceptions

In addition, CakePHP uses the following exceptions:

exception Cake\View\Exception\MissingViewException

The chosen view class could not be found.

exception Cake\View\Exception\MissingTemplateException

The chosen template file could not be found.

exception Cake\View\Exception\MissingLayoutException

The chosen layout could not be found.

exception Cake\View\Exception\MissingHelperException

The chosen helper could not be found.

exception Cake\View\Exception\MissingElementException

The chosen element file could not be found.

exception Cake\View\Exception\MissingCellException

The chosen cell class could not be found.

exception Cake\View\Exception\MissingCellViewException

The chosen cell view file could not be found.

exception Cake\Controller\Exception\MissingComponentException

A configured component could not be found.

exception Cake\Controller\Exception\MissingActionException

The requested controller action could not be found.

exception Cake\Controller\Exception\PrivateActionException

Accessing private/protected/_ prefixed actions.

exception Cake\Console\Exception\ConsoleException

A console library class encounter an error.

exception Cake\Console\Exception\MissingTaskException

A configured task could not found.

exception Cake\Console\Exception\MissingShellException

The shell class could not be found.

exception Cake\Console\Exception\MissingShellMethodException

The chosen shell class has no method of that name.

exception Cake\Database\Exception\MissingConnectionException

A model’s connection is missing.

exception Cake\Database\Exception\MissingDriverException

A database driver could not be found.

exception Cake\Database\Exception\MissingExtensionException

A PHP extension is missing for the database driver.

exception Cake\ORM\Exception\MissingTableException

A model’s table could not be found.

exception Cake\ORM\Exception\MissingEntityException

A model’s entity could not be found.

exception Cake\ORM\Exception\MissingBehaviorException

A model’s behavior could not be found.

exception Cake\ORM\Exception\PersistenceFailedException

An entity couldn’t be saved/deleted while using Cake\ORM\Table::saveOrFail() or Cake\ORM\Table::deleteOrFail().

New in version 3.4.1: PersistenceFailedException has been added.

exception Cake\Datasource\Exception\RecordNotFoundException

The requested record could not be found. This will also set HTTP response headers to 404.

exception Cake\Routing\Exception\MissingControllerException

The requested controller could not be found.

exception Cake\Routing\Exception\MissingRouteException

The requested URL cannot be reverse routed or cannot be parsed.

exception Cake\Routing\Exception\MissingDispatcherFilterException

The dispatcher filter could not be found.

exception Cake\Core\Exception\Exception

Base exception class in CakePHP. All framework layer exceptions thrown by CakePHP will extend this class.

These exception classes all extend Exception. By extending Exception, you can create your own ‘framework’ errors.

Cake\Core\Exception\Exception::responseHeader($header = null, $value = null)

See Cake\Network\Request::header()

All Http and Cake exceptions extend the Exception class, which has a method to add headers to the response. For instance when throwing a 405 MethodNotAllowedException the rfc2616 says:

"The response MUST include an Allow header containing a list of valid
methods for the requested resource."