Error Handling

CodeIgniter builds error reporting into your system through Exceptions, both the SPL collection, as well as a few exceptions that are provided by the framework.

Depending on your environment’s setup, the default action when an error or exception is thrown is to display a detailed error report unless the application is running under the production environment. In the production environment, a more generic message is displayed to keep the best user experience for your users.

Using Exceptions 

This section is a quick overview for newer programmers, or for developers who are not experienced with using exceptions.

What are Exceptions 

Exceptions are simply events that happen when the exception is “thrown”. This halts the current flow of the script, and execution is then sent to the error handler which displays the appropriate error page:

<?php

throw new \Exception('Some message goes here');

Catching Exceptions 

If you are calling a method that might throw an exception, you can catch that exception using a try/catch block:

<?php

try {
    $user = $userModel->find($id);
} catch (\Exception $e) {
    exit($e->getMessage());
}

If the $userModel throws an exception, it is caught and the code within the catch block is executed. In this example, the scripts dies, echoing the error message that the UserModel defined.

Catching Specific Exceptions

In the example above, we catch any type of Exception. If we only want to watch for specific types of exceptions, like a DataException, we can specify that in the catch parameter. Any other exceptions that are thrown and are not child classes of the caught exception will be passed on to the error handler:

<?php

use CodeIgniter\Database\Exceptions\DataException;

try {
    $user = $userModel->find($id);
} catch (DataException $e) {
    // do something here...
}

This can be handy for handling the error yourself, or for performing cleanup before the script ends. If you want the error handler to function as normal, you can throw a new exception within the catch block:

<?php

use CodeIgniter\Database\Exceptions\DataException;

try {
    $user = $userModel->find($id);
} catch (DataException $e) {
    // do something here...

    throw new \RuntimeException($e->getMessage(), $e->getCode(), $e);
}

Configuration 

Error Reporting 

By default, CodeIgniter will display a detailed error report with all errors in the development and testing environments, and will not display any errors in the production environment.

You can change your environment by setting the CI_ENVIRONMENT variable. See Setting Environment.

Important

Disabling error reporting DOES NOT stop logs from being written if there are errors.

Warning

Note that your settings from the .env file are added to $_SERVER and $_ENV. As a side effect, this means that if the detailed error report is displayed, your secure credentials are publicly exposed.

Logging Exceptions 

By default, all Exceptions other than “404 - Page Not Found” exceptions are logged. This can be turned on and off by setting the $log value of app/Config/Exceptions.php:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Exceptions extends BaseConfig
{
    // ...
    public bool $log = true;
    // ...
}

To ignore logging on other status codes, you can set the status code to ignore in the same file:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Exceptions extends BaseConfig
{
    // ...
    public array $ignoreCodes = [404];
    // ...
}

Note

It is possible that logging still will not happen for exceptions if your current Log settings are not set up to log critical errors, which all exceptions are logged as.

Logging Deprecation Warnings 

New in version 4.3.0.

Prior to v4.3.0, all errors reported by error_reporting() will be thrown as an ErrorException object.

But with the surge in use of PHP 8.1+, many users may see exceptions thrown for passing null to non-nullable arguments of internal functions.

To ease the migration to PHP 8.1, starting with v4.3.0, CodeIgniter has the feature that only logs the deprecation errors (E_DEPRECATED and E_USER_DEPRECATED) without throwing them as exceptions.

By default, CodeIgniter will only log deprecations without throwing exceptions in development environment. In production environment, no logging is done and no exceptions are thrown.

Configuration

The settings for this feature are as follows. First, make sure your copy of Config\Exceptions is updated with the two new properties and set as follows:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use Psr\Log\LogLevel;

class Exceptions extends BaseConfig
{
    // ...
    public bool $logDeprecations = true; // If set to false, an exception will be thrown.
    // ...
    public string $deprecationLogLevel = LogLevel::WARNING; // This should be one of the log levels supported by PSR-3.
    // ...
}

Next, depending on the log level you set in Config\Exceptions::$deprecationLogLevel, check whether the logger threshold defined in Config\Logger::$threshold covers the deprecation log level. If not, adjust it accordingly.

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Logger extends BaseConfig
{
    // ...
    // This must contain the log level (5 for LogLevel::WARNING) corresponding to $deprecationLogLevel.
    public $threshold = (ENVIRONMENT === 'production') ? 4 : 9;
    // ...
}

After that, subsequent deprecations will be logged as configured without throwing as exceptions.

This feature also works with user deprecations:

<?php

@trigger_error('Do not use this class!', E_USER_DEPRECATED);
// Your logs should contain a record with a message like: "[DEPRECATED] Do not use this class!"

For testing your application you may want to always throw on deprecations. You may configure this by setting the environment variable CODEIGNITER_SCREAM_DEPRECATIONS to a truthy value.

Framework Exceptions 

The following framework exceptions are available:

PageNotFoundException 

This is used to signal a 404, Page Not Found error:

<?php

use CodeIgniter\Exceptions\PageNotFoundException;

$page = $pageModel->find($id);

if ($page === null) {
    throw PageNotFoundException::forPageNotFound();
}

You can pass a message into the exception that will be displayed in place of the default message on the 404 page.

For the default 404 view file location, see HTTP Status Code and Error Views.

If, in app/Config/Routing.php or app/Config/Routes.php, you have specified a 404 Override, that will be called instead of the standard 404 page.

ConfigException 

This exception should be used when the values from the configuration class are invalid, or when the config class is not the right type, etc:

<?php

throw new \CodeIgniter\Exceptions\ConfigException();

This provides an exit code of 3.

DatabaseException 

This exception is thrown for database errors, such as when the database connection cannot be created, or when it is temporarily lost:

<?php

throw new \CodeIgniter\Database\Exceptions\DatabaseException();

This provides an exit code of 8.

RedirectException 

Note

Since v4.4.0, the namespace of RedirectException has been changed. Previously it was CodeIgniter\Router\Exceptions\RedirectException. The previous class is deprecated.

This exception is a special case allowing for overriding of all other response routing and forcing a redirect to a specific URI:

<?php

throw new \CodeIgniter\HTTP\Exceptions\RedirectException($uri);

$uri is a URI path relative to baseURL. You can also supply a redirect code to use instead of the default (302, “temporary redirect”):

<?php

throw new \CodeIgniter\HTTP\Exceptions\RedirectException($uri, 301);

Also, since v4.4.0 an object of a class that implements ResponseInterface can be used as the first argument. This solution is suitable for cases where you need to add additional headers or cookies in the response.

<?php

$response = service('response')
    ->redirect('https://example.com/path')
    ->setHeader('Some', 'header')
    ->setCookie('and', 'cookie');

throw new \CodeIgniter\HTTP\Exceptions\RedirectException($response);

Specify HTTP Status Code in Your Exception 

New in version 4.3.0.

Since v4.3.0, you can specify the HTTP status code for your Exception class to implement CodeIgniter\Exceptions\HTTPExceptionInterface.

When an exception implementing HTTPExceptionInterface is caught by CodeIgniter’s exception handler, the Exception code will become the HTTP status code.

HTTP Status Code and Error Views 

The exception handler displays the error view corresponding to the HTTP status code, if one exists.

For example, PageNotFoundException implements the HTTPExceptionInterface, so its exception code 404 will be the HTTP status code. Therefore if it is thrown, the system will show the error_404.php in the app/Views/errors/html folder when it is a web request. If it is invoked via CLI, the system will show the error_404.php in the app/Views/errors/cli folder.

If there is no view file corresponding to the HTTP status code, production.php or error_exception.php will be displayed.

Note

If display_errors is on in the PHP INI configuration, error_exception.php is selected and a detailed error report is displayed.

You should customize all of the error views in the app/Views/errors/html folder for your site.

You can also create error views for specific HTTP status code. For example, if you want to create an error view for “400 Bad Request”, add error_400.php.

Warning

If an error view file with the corresponding HTTP status code exists, the exception handler will display that file regardless of the environment. The view file must be implemented in such a way that it does not display detailed error messages in production environment by yourself.

Specify Exit Code in Your Exception 

New in version 4.3.0.

Since v4.3.0, you can specify the exit code for your Exception class to implement CodeIgniter\Exceptions\HasExitCodeInterface.

When an exception implementing HasExitCodeInterface is caught by CodeIgniter’s exception handler, the code returned from the getExitCode() method will become the exit code.

Custom Exception Handlers 

New in version 4.4.0.

If you need more control over how exceptions are displayed you can now define your own handlers and specify when they apply.

Defining the New Handler 

The first step is to create a new class which implements CodeIgniter\Debug\ExceptionHandlerInterface. You can also extend CodeIgniter\Debug\BaseExceptionHandler. This class includes a number of utility methods that are used by the default exception handler. The new handler must implement a single method: handle():

<?php

namespace App\Libraries;

use CodeIgniter\Debug\BaseExceptionHandler;
use CodeIgniter\Debug\ExceptionHandlerInterface;
use CodeIgniter\HTTP\RequestInterface;
use CodeIgniter\HTTP\ResponseInterface;
use Throwable;

class MyExceptionHandler extends BaseExceptionHandler implements ExceptionHandlerInterface
{
    // You can override the view path.
    protected ?string $viewPath = APPPATH . 'Views/exception/';

    public function handle(
        Throwable $exception,
        RequestInterface $request,
        ResponseInterface $response,
        int $statusCode,
        int $exitCode
    ): void {
        $this->render($exception, $statusCode, $this->viewPath . "error_{$statusCode}.php");

        exit($exitCode);
    }
}

This example defines the minimum amount of code typically needed - display a view and exit with the proper exit code. However, the BaseExceptionHandler provides a number of other helper functions and objects.

Configuring the New Handler 

Telling CodeIgniter to use your new exception handler class is done in the app/Config/Exceptions.php configuration file’s handler() method:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use CodeIgniter\Debug\ExceptionHandler;
use CodeIgniter\Debug\ExceptionHandlerInterface;
use Throwable;

class Exceptions extends BaseConfig
{
    // ...

    public function handler(int $statusCode, Throwable $exception): ExceptionHandlerInterface
    {
        return new ExceptionHandler($this);
    }
}

You can use any logic your application needs to determine whether it should handle the exception, but the two most common are checking on the HTTP status code or the type of exception. If your class should handle it then return a new instance of that class:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use CodeIgniter\Debug\ExceptionHandlerInterface;
use CodeIgniter\Exceptions\PageNotFoundException;
use Throwable;

class Exceptions extends BaseConfig
{
    // ...

    public function handler(int $statusCode, Throwable $exception): ExceptionHandlerInterface
    {
        if (in_array($statusCode, [400, 404, 500], true)) {
            return new \App\Libraries\MyExceptionHandler($this);
        }

        if ($exception instanceof PageNotFoundException) {
            return new \App\Libraries\MyExceptionHandler($this);
        }

        return new \CodeIgniter\Debug\ExceptionHandler($this);
    }
}