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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.

Configuration ​

Error configuration is done in your application's config/app.php file. By default CakePHP uses Cake\Error\ErrorTrap and Cake\Error\ExceptionTrap to handle both PHP errors and exceptions respectively. 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. See Deprecation Warnings 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.
  • logger (prior to 4.4.0 use errorLogger) -Cake\Error\ErrorLoggerInterface - The class responsible for logging errors and unhandled exceptions. Defaults to Cake\Error\ErrorLogger.
  • errorRenderer - Cake\Error\ErrorRendererInterface - The class responsible for rendering errors. Default is chosen based on PHP SAPI.
  • ignoredDeprecationPaths - array - A list of glob compatible paths that deprecation errors should be ignored in. Added in 4.2.0

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.

Deprecation Warnings ​

CakePHP uses deprecation warnings to indicate when features have been deprecated. We also recommend this system for use in your plugins and application code when useful. You can trigger deprecation warnings with deprecationWarning():

text
deprecationWarning('5.0', 'The example() method is deprecated. Use getExample() instead.');

When upgrading CakePHP or plugins you may encounter new deprecation warnings. You can temporarily disable deprecation warnings in one of a few ways:

  1. Using the Error.errorLevel setting to E_ALL ^ E_USER_DEPRECATED to ignore all deprecation warnings.

  2. Using the Error.ignoredDeprecationPaths configuration option to ignore deprecations with glob compatible expressions. For example:

    text
    'Error' => [
    'ignoredDeprecationPaths' => [
        'vendors/company/contacts/*',
        'src/Models/*',
    ],
],

    Would ignore all deprecations from your Models directory and the Contacts plugin in your application.

Changing Exception Handling ​

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

  1. Listen to events This allows you to be notified through CakePHP events when errors and exceptions have been handled.
  2. Custom templates This allows you to change the rendered view templates as you would any other template in your application.
  3. Custom Controller This allows you to control how exception pages are rendered.
  4. Custom ExceptionRenderer This allows you to control how exception pages and logging are performed.
  5. Create & register your own traps This gives you complete control over how errors & exceptions are handled, logged and rendered. Use Cake\Error\ExceptionTrap and Cake\Error\ErrorTrap as reference when implementing your traps.

Listen to Events ​

The ErrorTrap and ExceptionTrap handlers will trigger CakePHP events when they handle errors. You can listen to the Error.beforeRender event to be notified of PHP errors. The Exception.beforeRender event is dispatched when an exception is handled:

php
$errorTrap = new ErrorTrap(Configure::read('Error'));
$errorTrap->getEventManager()->on(
    'Error.beforeRender',
    function (EventInterface $event, PhpError $error) {
        // do your thing
    }
);

Within an Error.beforeRender handler you have a few options:

  • Stop the event to prevent rendering.
  • Return a string to skip rendering and use the provided string instead

Within an Exception.beforeRender handler you have a few options:

  • Stop the event to prevent rendering.
  • Set the exception data attribute with setData('exception', $err) to replace the exception that is being rendered.
  • Return a response from the event listener to skip rendering and use the provided response instead.

Custom Templates ​

The default exception trap renders all uncaught exceptions your application raises with the help of Cake\Error\Renderer\WebExceptionRenderer, and your application's ErrorController.

The error page views are located at templates/Error/. All 4xx errors use the error400.php template, and 5xx errors use the error500.php. 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\CakeException 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.

Custom Error Page Layout ​

By default error templates use templates/layout/error.php for a layout. You can use the layout property to pick a different layout:

php
// inside templates/Error/error400.php
$this->layout = 'my_error';

The above would use templates/layout/my_error.php 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.php or error500.php based on their status code.

Custom Controller ​

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.

If your application uses Prefix Routing you can create custom error controllers for each routing prefix. For example, if you had an Admin prefix. You could create the following class:

php
namespace App\Controller\Admin;

use App\Controller\AppController;
use Cake\Event\EventInterface;

class ErrorController extends AppController
{
    /**
     * beforeRender callback.
     *
     * @param \Cake\Event\EventInterface $event Event.
     * @return void
     */
    public function beforeRender(EventInterface $event): void
    {
        $this->viewBuilder()->setTemplatePath('Error');
    }
}

This controller would only be used when an error is encountered in a prefixed controller, and allows you to define prefix specific logic/templates as needed.

Exception specific logic ​

Within your controller you can define public methods to handle custom application errors. For example a MissingWidgetException would be handled by a missingWidget() controller method, and CakePHP would use templates/Error/missing_widget.php as the template. For example:

php
namespace App\Controller\Admin;

use App\Controller\AppController;
use Cake\Event\EventInterface;

class ErrorController extends AppController
{
    protected function missingWidget(MissingWidgetException $exception)
    {
        // You can prepare additional template context or trap errors.
    }
}

Added in version 5.2.0

Exception specific controller methods and templates were added.

Custom 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 change the logic used to create an error controller, choose the template, or control the overall rendering process.

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:

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

use Cake\Error\Renderer\WebExceptionRenderer;

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

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

// In Application::middleware()
$middlewareQueue->add(new ErrorHandlerMiddleware(
    ['exceptionRenderer' => AppExceptionRenderer::class] + Configure::read('Error'),
    $this,
));
// ...

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:

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

use Cake\Error\Renderer\WebExceptionRenderer;

class AppExceptionRenderer extends WebExceptionRenderer
{
    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:

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

use App\Controller\SuperCustomErrorController;
use Cake\Controller\Controller;
use Cake\Error\Renderer\WebExceptionRenderer;

class AppExceptionRenderer extends WebExceptionRenderer
{
    protected function _getController(): Controller
    {
        return new SuperCustomErrorController();
    }
}

// In Application::middleware()
$middlewareQueue->add(new ErrorHandlerMiddleware(
    ['exceptionRenderer' => AppExceptionRenderer::class] + Configure::read('Error'),
    $this,
));
// ...

application exceptions

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:

php
use Cake\Core\Exception\CakeException;

class MissingWidgetException extends CakeException
{
}

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

Exceptions that subclass Cake\Http\Exception\HttpException, will have their error code used as an HTTP status code if the error code is between 400 and 506.

The constructor for Cake\Core\Exception\CakeException 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:

php
use Cake\Core\Exception\CakeException;

class MissingWidgetException extends CakeException
{
    // 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..

NOTE

Prior to CakePHP 4.2.0 use class Cake\Core\Exception\Exception instead of Cake\Core\Exception\CakeException

Logging Exceptions ​

Using the built-in exception handling, you can log all the exceptions that are dealt with by ErrorTrap 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

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Used for doing 400 Bad Request error.

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Used for doing a 401 Unauthorized error.

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Used for doing a 403 Forbidden error.

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

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Used for doing a 404 Not found error.

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Used for doing a 405 Method Not Allowed error.

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Used for doing a 406 Not Acceptable error.

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Used for doing a 409 Conflict error.

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Used for doing a 410 Gone error.

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

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Used for doing a 500 Internal Server Error.

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Used for doing a 501 Not Implemented Errors.

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Used for doing a 503 Service Unavailable error.

For more details on HTTP 5xx error status codes see 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:

php
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->viewBuilder()->setOption('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:

php
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->viewBuilder()->setOption('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:

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The chosen view class could not be found.

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The chosen template file could not be found.

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The chosen layout could not be found.

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The chosen helper could not be found.

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The chosen element file could not be found.

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The chosen cell class could not be found.

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The chosen cell view file could not be found.

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A configured component could not be found.

nocontentsentry

The requested controller action could not be found.

nocontentsentry

Accessing private/protected/_ prefixed actions.

nocontentsentry

A console library class encounter an error.

nocontentsentry

A model's connection is missing.

nocontentsentry

A database driver could not be found.

nocontentsentry

A PHP extension is missing for the database driver.

nocontentsentry

A model's table could not be found.

nocontentsentry

A model's entity could not be found.

nocontentsentry

A model's behavior could not be found.

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

nocontentsentry

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

nocontentsentry

The requested controller could not be found.

nocontentsentry

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

nocontentsentry

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.

method Class::responseHeader($header = null, $value = null)

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."

Customizing PHP Error Handling ​

By default PHP errors are rendered to console or HTML output, and also logged. If necessary, you can swap out CakePHP's error handling logic with your own.

Custom Error Logging ​

Error handlers use instances of Cake\Error\ErrorLoggingInterface to create log messages and log them to the appropriate place. You can replace the error logger using the Error.errorLogger configure value. An example error logger:

php
namespace App\Error;

use Cake\Error\ErrorLoggerInterface;
use Cake\Error\PhpError;
use Psr\Http\Message\ServerRequestInterface;
use Throwable;

/**
 * Log errors and unhandled exceptions to `Cake\Log\Log`
 */
class ErrorLogger implements ErrorLoggerInterface
{
    /**
     * @inheritDoc
     */
    public function logError(
        PhpError $error,
        ?ServerRequestInterface $request,
        bool $includeTrace = false
    ): void {
        // Log PHP Errors
    }

    /**
     * @inheritDoc
     */
    public function logException(
        ?ServerRequestInterface $request,
        bool $includeTrace = false
    ): void {
        // Log exceptions.
    }
}

Custom Error Rendering ​

CakePHP includes error renderers for both web and console environments. If however, you would like to replace the logic that renders errors you can create a class:

php
// src/Error/CustomErrorRenderer.php
namespace App\Error;

use Cake\Error\ErrorRendererInterface;
use Cake\Error\PhpError;

class CustomErrorRenderer implements ErrorRendererInterface
{
    public function write(string $out): void
    {
        // output the rendered error to the appropriate output stream
    }

    public function render(PhpError $error, bool $debug): string
    {
        // Convert the error into the output string.
    }
}

The constructor of your renderer will be passed an array of all the Error configuration. You connect your custom error renderer to CakePHP via the Error.errorRenderer config value. When replacing error handling you will need to account for both web and command line environments.

Released under the MIT License.

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