silverstripe-framework/docs/en/topics/controller.md

# Controller

Base controller class.  You will extend this to take granular control over the 
actions and url handling of aspects of your SilverStripe site.

## Usage

The following example is for a simple `[api:Controller]` class. If you're using
the cms module and looking at Page_Controller instances you won't need to setup
your own routes since the cms module handles these routes.

`mysite/code/Controllers/FastFood.php`

	:::php
	<?php
	
	class FastFood_Controller extends Controller {
		public static $allowed_actions = array('order');
	    public function order(SS_HTTPRequest $request) {
	        print_r($arguments);
	    }
	}

## Routing

`mysite/_config/routes.yml`

	:::yaml
	---
	Name: myroutes
	After: framework/routes#coreroutes
	---
	Director:
	  rules:
	    'fastfood/$Action/$ID/$Name': 'FastFood_Controller'


Request for `/fastfood/order/24/cheesefries` would result in the following to 
the $arguments above. If needed, use `?flush=1` on the end of request after 
making any code changes to your controller.

	:::ss
	Array
	(
	    [Action] => order
	    [ID] => 24
	    [Name] => cheesefries
	)

<div class="warning" markdown='1'>
	SilverStripe automatically adds a URL routing entry based on the controller's class name,
	so a `MyController` class is accessible through `http://yourdomain.com/MyController`.
</div>

## Access Control

### Through $allowed_actions

All public methods on a controller are accessible by their name through the `$Action`
part of the URL routing, so a `MyController->mymethod()` is accessible at
`http://yourdomain.com/MyController/mymethod`. This is not always desireable,
since methods can return internal information, or change state in a way
that's not intended to be used through a URL endpoint.

SilverStripe strongly recommends securing your controllers
through defining a `$allowed_actions` array on the class,
which allows whitelisting of methods, as well as a concise
way to perform checks against permission codes or custom logic.

	:::php
	class MyController extends Controller {
		public static $allowed_actions = array(
			// someaction can be accessed by anyone, any time
			'someaction', 
			// So can otheraction
			'otheraction' => true, 
			// restrictedaction can only be people with ADMIN privilege
			'restrictedaction' => 'ADMIN', 
			// complexaction can only be accessed if $this->canComplexAction() returns true
			'complexaction' '->canComplexAction' 
		);
	}

There's a couple of rules guiding these checks:

 * Each class is only responsible for access control on the methods it defines
 * If `$allowed_actions` is defined as an empty array, no actions are allowed
 * If `$allowed_actions` is undefined, all public methods on the specific class are allowed 
   (not recommended)
 * Access checks on parent classes need to be overwritten via the Config API
 * Only public methods can be made accessible
 * If a method on a parent class is overwritten, access control for it has to be redefined as well
 * An action named "index" is whitelisted by default, 
   unless allowed_actions is defined as an empty array,
   or the action is specifically restricted in there.
 * Methods returning forms also count as actions which need to be defined
 * Form action methods (targets of `FormAction`) should NOT be included in `$allowed_actions`,
   they're handled separately through the form routing (see the ["forms" topic](/topics/forms))
 * `$allowed_actions` can be defined on `Extension` classes applying to the controller.

If the permission check fails, SilverStripe will return a "403 Forbidden" HTTP status.

### Through the action

Each method responding to a URL can also implement custom permission checks,
e.g. to handle responses conditionally on the passed request data.

	:::php
	class MyController extends Controller {
		public static $allowed_actions = array('myaction');
		public function myaction($request) {
			if(!$request->getVar('apikey')) {
				return $this->httpError(403, 'No API key provided');
			} 
				
			return 'valid';
		}
	}

Unless you transform the response later in the request processing,
it'll look pretty ugly to the user. Alternatively, you can use
`ErrorPage::response_for(<status-code>)` to return a more specialized layout.

Note: This is recommended as an addition for `$allowed_actions`, in order to handle
more complex checks, rather than a replacement.

### Through the init() method

After checking for allowed_actions, each controller invokes its `init()` method,
which is typically used to set up common state in the controller, and 
include JavaScript and CSS files in the output which are used for any action.
If an `init()` method returns a `SS_HTTPResponse` with either a 3xx or 4xx HTTP
status code, it'll abort execution. This behaviour can be used to implement
permission checks.

	:::php
	class MyController extends Controller {
		public static $allowed_actions = array();
		public function init() {
			parent::init();
			if(!Permission::check('ADMIN')) return $this->httpError(403);
		}
	}

## URL Handling

In the above example the URLs were configured using the `[api:Director]` rules 
in the **routes.yml** file. Alternatively you can specify these in your 
Controller class via the **$url_handlers** static array (which gets processed 
by the `[api:RequestHandler]`).  

This is useful when you want to subvert the fixed action mapping of `fastfood/order/*` 
to the function **order**. In the case below we also want any orders coming 
through `/fastfood/drivethrough/` to use the same order function.

`mysite/code/Controllers/FastFood.php`

	:::php
	class FastFood_Controller extends Controller {
	    private static $allowed_actions = array('drivethrough');
	    public static $url_handlers = array(
	        'drivethrough/$Action/$ID/$Name' => 'order'
	    );

## Access Control

### Through $allowed_actions

 * If `$allowed_actions` is undefined, `null` or `array()`, no actions are accessible
 * Each class is only responsible for access control on the methods it defines
 * Access checks on parent classes need to be overwritten via the Config API
 * Only public methods can be made accessible
 * If a method on a parent class is overwritten, access control for it has to be redefined as well
 * An action named "index" is whitelisted by default
 * Methods returning forms also count as actions which need to be defined
 * Form action methods (targets of `FormAction`) should NOT be included in `$allowed_actions`,
   they're handled separately through the form routing (see the ["forms" topic](/topics/forms))
 * `$allowed_actions` can be defined on `Extension` classes applying to the controller.

## URL Patterns

The `[api:RequestHandler]` class will parse all rules you specify against the 
following patterns.

**A rule must always start with alphabetical ([A-Za-z]) characters or a $Variable 
declaration**

 | Pattern     | Description | 
 | ----------- | --------------- | 
 | `$`         | **Param Variable** - Starts the name of a paramater variable, it is optional to match this unless ! is used | 
 | `!`         | **Require Variable** - Placing this after a parameter variable requires data to be present for the rule to match | 
 | `//`        | **Shift Point** - Declares that only variables denoted with a $ are parsed into the $params AFTER this point in the regex | 

## Examples

See maetl's article in the Links below of a detailed explanation. 

`$Action/$ID/$OtherID` - Standard URL handler for a Controller.  Take whatever `URLSegment` it is set to, find
the Action to match a function in the controller, and parse two optional `$param` variables that will be named `ID` and
`OtherID`.


`admin/help//$Action/$ID` - Match an url starting with `/admin/help/`, but don't include `/help/` as part of the
action (the shift point is set to start parsing variables and the appropriate controller action AFTER the `//`)


`tag/$Tag!` - Match an URL starting with `/tag/` after the controller's `URLSegment` and require it to have something
after it.  If the URLSegment is **order** then `/order/tag/34` and `/order/tag/asdf` match but `/order/tag/` will not


You can use the `debug_request=1` switch from the [urlvariabletools](/reference/urlvariabletools) to see these in action.

## Redirection

Controllers facilitate HTTP redirection.

Note: These methods have been formerly located on the `[api:Director]` class.

*  `redirect("action-name")`: If there's no slash in the URL passed to redirect, then it is assumed that you want to go to a different action on the current controller.
*  `redirect("relative/url")`: If there is a slash in the URL, it's taken to be a normal URL.  Relative URLs
will are assumed to be relative to the site-root.
*  `redirect("http://www.absoluteurl.com")`: Of course, you can pass `redirect()` absolute URLs too.
*  `redirectBack()`: This will return you to the previous page.

The `redirect()` method takes an optional HTTP status code,
either `301` for permanent redirects, or `302` for temporary redirects (default).

## Access control

You can also limit access to actions on a controller using the static `$allowed_actions` array. This allows you to always allow an action, or restrict it to a specific permission or to call a method that checks if the action is allowed.

For example, the default `Controller::$allowed_actions` is
	private static $allowed_actions = array(
		'handleAction',
		'handleIndex',
	);
which allows the `handleAction` and `handleIndex` methods to be called via a URL.

To allow any action on your controller to be called you can either leave your `$allowed_actions` array empty or not have one at all. This is the default behaviour, however it is not recommended as it allows anything on your controller to be called via a URL, including view-specific methods.

The recommended approach is to explicitly state the actions that can be called via a URL. Any action not in the `$allowed_actions` array, excluding the default `index` method, is then unable to be called.

To always allow an action to be called, you can either add the name of the action to the array or add a value of `true` to the array, using the name of the method as its index. For example
	private static $allowed_actions = array(
		'MyAwesomeAction',
		'MyOtherAction' => true
	);


To require that the current user has a certain permission before being allowed to call an action you add the action to the array as an index with the value being the permission code that user must have. For example
	private static $allowed_actions = array(
		'MyAwesomeAction',
		'MyOtherAction' => true,
		'MyLimitedAction' => 'CMS_ACCESS_CMSMain',
		'MyAdminAction' => 'ADMIN'
	);

If neither of these are enough to decide if an action should be called, you can have the check use a method. The method must be on the controller class and return true if the action is allowed or false if it isn't. To do this add the action to the array as an index with the value being the name of the method to called preceded by '->'. You are able to pass static arguments to the method in much the same way as you can with extensions. Strings are enclosed in quotes, numeric values are written as numbers and true and false are written as true and false. For example
	private static $allowed_actions = array(
		'MyAwesomeAction',
		'MyOtherAction' => true,
		'MyLimitedAction' => 'CMS_ACCESS_CMSMain',
		'MyAdminAction' => 'ADMIN',
		'MyRestrictedAction' => '->myCheckerMethod("MyRestrictedAction", false, 42)',
		'MyLessRestrictedAction' => '->myCheckerMethod'
	);

In this example, `MyAwesomeAction` and `MyOtherAction` are always allowed, `MyLimitedAction` requires access to the CMS for the current user and `MyAdminAction` requires the current user to be an admin. `MyRestrictedAction` calls the method `myCheckerMethod`, passing in the string "MyRestrictedAction", the boolean false and the number 42. `MyLessRestrictedAction` simply calls the method `myCheckerMethod` with no arguments.

## API Documentation

`[api:Controller]`

## Links

*  `[api:Director]` class
*  [execution-pipeline](/reference/execution-pipeline)
*  [URL Handling in Controllers](http://maetl.net/silverstripe-url-handling) by maetl