Controller Filters

Creating a Filter
- Before Filters
- After Filters
Configuring Filters
- $aliases
- $globals
- $methods
- $filters
Confirming Filters
- filter:check
Provided Filters
- InvalidChars
- SecureHeaders

Controller Filters allow you to perform actions either before or after the controllers execute. Unlike events, you can choose the specific URIs or routes in which the filters will be applied to. Before filters may modify the Request while after filters can act on and even modify the Response, allowing for a lot of flexibility and power.

Some common examples of tasks that might be performed with filters are:

Performing CSRF protection on the incoming requests
Restricting areas of your site based upon their Role
Perform rate limiting on certain endpoints
Display a “Down for Maintenance” page
Perform automatic content negotiation
and more…

Creating a Filter 

Filters are simple classes that implement CodeIgniter\Filters\FilterInterface. They contain two methods: before() and after() which hold the code that will run before and after the controller respectively. Your class must contain both methods but may leave the methods empty if they are not needed. A skeleton filter class looks like:

<?php

namespace App\Filters;

use CodeIgniter\Filters\FilterInterface;
use CodeIgniter\HTTP\RequestInterface;
use CodeIgniter\HTTP\ResponseInterface;

class MyFilter implements FilterInterface
{
    public function before(RequestInterface $request, $arguments = null)
    {
        // Do something here
    }

    public function after(RequestInterface $request, ResponseInterface $response, $arguments = null)
    {
        // Do something here
    }
}

Before Filters 

Replacing Request

From any filter, you can return the $request object and it will replace the current Request, allowing you to make changes that will still be present when the controller executes.

Stopping Later Filters

Also, when you have a series of filters you may also want to stop the execution of the later filters after a certain filter. You can easily do this by returning any non-empty result. If the before filter returns an empty result, the controller actions or the later filters will still be executed.

An exception to the non-empty result rule is the Request instance. Returning it in the before filter will not stop the execution but only replace the current $request object.

Returning Response

Since before filters are executed prior to your controller being executed, you may at times want to stop the actions in the controller from happening.

This is typically used to perform redirects, like in this example:

<?php

namespace App\Filters;

use CodeIgniter\Filters\FilterInterface;
use CodeIgniter\HTTP\RequestInterface;
use CodeIgniter\HTTP\ResponseInterface;

class MyFilter implements FilterInterface
{
    public function before(RequestInterface $request, $arguments = null)
    {
        $auth = service('auth');

        if (! $auth->isLoggedIn()) {
            return redirect()->to(site_url('login'));
        }
    }
}

If a Response instance is returned, the Response will be sent back to the client and script execution will stop. This can be useful for implementing rate limiting for APIs. See Throttler for an example.

After Filters 

After filters are nearly identical to before filters, except that you can only return the $response object, and you cannot stop script execution. This does allow you to modify the final output, or simply do something with the final output. This could be used to ensure certain security headers were set the correct way, or to cache the final output, or even to filter the final output with a bad words filter.

Configuring Filters 

There are two ways to configure filters when they get run. One is done in app/Config/Filters.php, the other is done in app/Config/Routes.php.

If you want to specify filter to a specific route, use app/Config/Routes.php and see URI Routing.

The filters that are specified to a route (in app/Config/Routes.php) are executed before the filters specified in app/Config/Filters.php.

Note

The safest way to apply filters is to disable auto-routing, and set filters to routes.

The app/Config/Filters.php file contains four properties that allow you to configure exactly when the filters run.

Warning

It is recommended that you should always add * at the end of a URI in the filter settings. Because a controller method might be accessible by different URLs than you think. For example, when Auto Routing (Legacy) is enabled, if you have Blog::index, it can be accessible with blog, blog/index, and blog/index/1, etc.

$aliases 

The $aliases array is used to associate a simple name with one or more fully-qualified class names that are the filters to run:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    public array $aliases = [
        'csrf' => \CodeIgniter\Filters\CSRF::class,
    ];

    // ...
}

Aliases are mandatory and if you try to use a full class name later, the system will throw an error. Defining them in this way makes it simple to switch out the class used. Great for when you decided you need to change to a different authentication system since you only change the filter’s class and you’re done.

You can combine multiple filters into one alias, making complex sets of filters simple to apply:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    public array $aliases = [
        'apiPrep' => [
            \App\Filters\Negotiate::class,
            \App\Filters\ApiAuth::class,
        ],
    ];

    // ...
}

You should define as many aliases as you need.

$globals 

The second section allows you to define any filters that should be applied to every request made by the framework. You should take care with how many you use here, since it could have performance implications to have too many run on every request. Filters can be specified by adding their alias to either the before or after array:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    // ...

    public array $globals = [
        'before' => [
            'csrf',
        ],
        'after' => [],
    ];

    // ...
}

Except for a Few URIs

There are times where you want to apply a filter to almost every request, but have a few that should be left alone. One common example is if you need to exclude a few URI’s from the CSRF protection filter to allow requests from third-party websites to hit one or two specific URI’s, while keeping the rest of them protected. To do this, add an array with the except key and a URI path (relative to BaseURL) to match as the value alongside the alias:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    // ...

    public array $globals = [
        'before' => [
            'csrf' => ['except' => 'api/*'],
        ],
        'after' => [],
    ];

    // ...
}

Any place you can use a URI path (relative to BaseURL) in the filter settings, you can use a regular expression or, like in this example, use an asterisk (*) for a wildcard that will match all characters after that. In this example, any URI path starting with api/ would be exempted from CSRF protection, but the site’s forms would all be protected. If you need to specify multiple URI paths, you can use an array of URI path patterns:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    // ...

    public array $globals = [
        'before' => [
            'csrf' => ['except' => ['foo/*', 'bar/*']],
        ],
        'after' => [],
    ];

    // ...
}

$methods 

Warning

If you use $methods filters, you should disable Auto Routing (Legacy) because Auto Routing (Legacy) permits any HTTP method to access a controller. Accessing the controller with a method you don’t expect could bypass the filter.

You can apply filters to all requests of a certain HTTP method, like POST, GET, PUT, etc. In this array, you would specify the method name in lowercase. It’s value would be an array of filters to run:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    // ...

    public array $methods = [
        'post' => ['InvalidChars', 'csrf'],
        'get'  => ['csrf'],
    ];

    // ...
}

Note

Unlike the $globals or the $filters properties, these will only run as before filters.

In addition to the standard HTTP methods, this also supports one special case: cli. The cli method would apply to all requests that were run from the command line.

$filters 

This property is an array of filter aliases. For each alias, you can specify before and after arrays that contain a list of URI path (relative to BaseURL) patterns that filter should apply to:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    // ...

    public array $filters = [
        'foo' => ['before' => ['admin/*'], 'after' => ['users/*']],
        'bar' => ['before' => ['api/*', 'admin/*']],
    ];

    // ...
}

Filter Arguments

New in version 4.4.0.

When configuring $filters, additional arguments may be passed to a filter:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    // ...

    public $filters = [
        'group:admin,superadmin'  => ['before' => ['admin/*']],
        'permission:users.manage' => ['before' => ['admin/users/*']],
    ];

    // ...
}

In this example, when the URI matches admin/*', the array ['admin', 'superadmin'] will be passed in $arguments to the group filter’s before() methods. When the URI matches admin/users/*', the array ['users.manage'] will be passed in $arguments to the permission filter’s before() methods.

Confirming Filters 

CodeIgniter has the following command to check the filters for a route.

filter:check 

New in version 4.3.0.

Check the filters for the route / with GET method:

php spark filter:check get /

The output is like the following:

+--------+-------+----------------+---------------+
| Method | Route | Before Filters | After Filters |
+--------+-------+----------------+---------------+
| GET    | /     |                | toolbar       |
+--------+-------+----------------+---------------+

You can also see the routes and filters by the spark routes command. See URI Routing.

Provided Filters 

The filters bundled with CodeIgniter4 are: Honeypot, CSRF, InvalidChars, SecureHeaders, and DebugToolbar.

Note

The filters are executed in the order defined in the config file. However, if enabled, DebugToolbar is always executed last because it should be able to capture everything that happens in the other filters.

InvalidChars 

This filter prohibits user input data ($_GET, $_POST, $_COOKIE, php://input) from containing the following characters:

invalid UTF-8 characters
control characters except line break and tab code

SecureHeaders 

This filter adds HTTP response headers that your application can use to increase the security of your application.

If you want to customize the headers, extend CodeIgniter\Filters\SecureHeaders and override the $headers property. And change the $aliases property in app/Config/Filters.php:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;

class Filters extends BaseConfig
{
    public array $aliases = [
        // ...
        'secureheaders' => \App\Filters\SecureHeaders::class,
    ];

    // ...
}

If you want to know about secure headers, see OWASP Secure Headers Project.