yii2/docs/guide/runtime-routing.md

Routing and URL Creation

Note: This section is under development.

When a Yii application starts processing a requested URL, the first step it does is to parse the URL into a route. The route is then used to instantiate the corresponding controller action to handle the request. This whole process is called routing.

The reverse process of routing is called URL creation, which creates a URL from a given route and the associated parameters. When the created URL is later requested, the routing process can resolve it back into the original route and parameters.

The central piece responsible for routing and URL creation is the yii\web\UrlManager, which is registered as the urlManager application component. The yii\web\UrlManager provides the yii\web\UrlManager::parseRequest() method to parse an incoming request into a route and the associated parameters and the yii\web\UrlManager::createUrl() method to create a URL from a given route and its associated parameters.

By configuring the urlManager component in the application configuration, you can let your application to recognize arbitrary URL formats without modifying your existing application code. For example, you can use the following code to create a URL for the post/view action:

use yii\helpers\Url;

// Url::to() calls UrlManager::createUrl() to create a URL
$url = Url::to(['post/view', 'id' => 100]);

Depending on the urlManager configuration, the created URL may look like one of the followings (or other format). And if the created URL is requested later, it will still be parsed back into the original route and parameter value.

/index.php?r=post/view&id=100
/index.php/post/100
/posts/100

URL Formats

The yii\web\UrlManager supports two URL formats: the default URL format and the pretty URL format.

The default URL format uses a query parameter named r to represent the route and normal query parameters to represent the parameters associated with the route. For example, the URL /index.php?r=post/view&id=100 represents the route post/view and the id parameter 100. The default URL format does not require any configuration about the yii\web\UrlManager and works in any Web server setup.

The pretty URL format uses the extra path following the entry script name to represent the route and the associated parameters. For example, the extra path in the URL /index.php/post/100 is /post/100 which may represent the route post/view and the id parameter 100 with a proper yii\web\UrlManager::rules. To use the pretty URL format, you will need to design a set of yii\web\UrlManager::rules according to the actual requirement about how the URLs should look like.

You may switch between the two URL formats by toggling the yii\web\UrlManager::enablePrettyUrl property of the yii\web\UrlManager without changing any other application code.

Routing

Routing involves two steps. In the first step, the incoming request is parsed into a route and the associated parameters. In the second step, a controller action corresponding to the parsed route is created to handle the request.

When using the default URL format, parsing a request into a route is as simple as getting the value of a GET parameter named r. When using the pretty URL format, however, it requires examining the registered yii\web\UrlManager::rules to find one that can resolve the request into a route. If such a rule cannot be found, a yii\web\NotFoundHttpException exception will be thrown.

Once the request is parsed into a route, it is time to create the controller action identified by the route. The route is broken down into multiple parts by the slashes in it. For example, site/index will be broken into site and index. Each part is an ID which may refer to a module, a controller or an action. Starting from the first part in the route, the application conducts the following steps to create modules (if any), the controller and the action:

1. Set the application as the current module.
2. Check if the yii\base\Module::controllerMap of the current module contains the current ID. If so, a controller object will be created according to the controller configuration found in the map, and Step 5 will be taken to handle the rest part of the route.
3. Check if the ID refers to a module listed in the yii\base\Module::modules property of the current module. If so, a module is created according to the configuration found in the module list, and Step 2 will be taken to handle the next part of the route under the context of the newly created module.
4. Treat the ID as a controller ID and create a controller object. Do the next step with the rest part of the route.
5. The controller looks for the current ID in its yii\base\Controller::actions(). If found, it creates an action according to the configuration found in the map. Otherwise, the controller will attempt to create an inline action which is defined by an action method corresponding to the current ID.

Among the above steps, if any error occurs, a yii\web\NotFoundHttpException will be thrown, indicating failure of the routing process.

Default Route

When a request is parsed into an empty route, the so-called default route will be used, instead. By default, the default route is site/index, which refers to the index action of the site controller. You may customize customize it by configuring the yii\web\Application::defaultRoute property of the application in the application configuration like the following:

[
    // ...
    'defaultRoute' => 'main/index',
];

catchAll Route

Sometimes, you may want to put your Web application in maintenance mode temporarily and display the same informational page for all requests. There are many ways to accomplish this goal. But one of the simplest ways is to configure the yii\web\Application::catchAll property like the following in the application configuration:

[
    // ...
    'catchAll' => ['site/offline'],
];

With the above configuration, the site/offline action will be used to handle all incoming requests.

The catchAll property should take an array whose first element specifies a route, and the rest of the elements (name-value pairs) specify the parameters to be bound to the action.

Creating URLs

Yii provides a helper method yii\helpers\Url::to() to create various kinds of URLs from given routes and their associated parameters. For example,

use yii\helpers\Url;

// creates a URL to a route: /index.php?r=post/index
echo Url::to(['post/index']);

// creates a URL to a route with parameters: /index.php?r=post/view&id=100
echo Url::to(['post/view', 'id' => 100]);

// creates an anchored URL: /index.php?r=post/view&id=100#content
echo Url::to(['post/view', 'id' => 100, '#' => 'content']);

// creates an absolute URL: http://www.example.com/index.php?r=post/index
echo Url::to(['post/index'], true);

// creates an absolute URL using https scheme: https://www.example.com/index.php?r=post/index
echo Url::to(['post/index'], 'https');

Note that in the above example, we assume the default URL format is being used. If the pretty URL format is enabled, the created URLs will be different, according to the yii\web\UrlManager::rules in use.

The route passed to the yii\helpers\Url::to() method is context sensitive. It can be either a relative route or an absolute route which will be normalized according to the following rules:

• If the route is an empty string, the currently requested yii\web\Controller::route will be used;
• If the route contains no slashes at all, it is considered to be an action ID of the current controller and will be prepended with the \yii\web\Controller::uniqueId value of the current controller;
• If the route has no leading slash, it is considered to be a route relative to the current module and will be prepended with the \yii\base\Module::uniqueId value of the current module.

For example, assume the current module is admin and the current controller is post,

use yii\helpers\Url;

// currently requested route: /index.php?r=admin/post/index
echo Url::to(['']);

// a relative route with action ID only: /index.php?r=admin/post/index
echo Url::to(['index']);

// a relative route: /index.php?r=admin/post/index
echo Url::to(['post/index']);

// an absolute route: /index.php?r=post/index
echo Url::to(['/post/index']);

The yii\helpers\Url::to() method is implemented by calling the yii\web\UrlManager::createUrl() and yii\web\UrlManager::createAbsoluteUrl() methods of the yii\web\UrlManager. In the next few subsections, we will explain how to configure the yii\web\UrlManager to customize the format of the created URLs.

The yii\helpers\Url::to() method also supports creating URLs that are NOT related with particular routes. Instead of passing an array as its first parameter, you should pass a string in this case. For example,

use yii\helpers\Url;

// currently requested URL: /index.php?r=admin/post/index
echo Url::to();

// an aliased URL: http://example.com
Yii::setAlias('@example', 'http://example.com/');
echo Url::to('@example');

// an absolute URL: http://example.com/images/logo.gif
echo Url::to('/images/logo.gif', true);

Besides the to() method, the yii\helpers\Url` helper class also provides several other convenient URL creation methods. For example,

use yii\helpers\Url;

// home page URL: /index.php?r=site/index
echo Url::home();

// the base URL, useful if the application is deployed in a sub-folder of the Web root
echo Url::base();

// the canonical URL of the currently requested URL
// see https://en.wikipedia.org/wiki/Canonical_link_element
echo Url::canonical();

// remember the currently requested URL and retrieve it back in later requests
Url::remember();
echo Url::previous();

Using Pretty URLs

To use pretty URLs, configure the urlManager component in the application configuration like the following:

[
    'components' => [
        'urlManager' => [
            'enablePrettyUrl' => true,
            'showScriptName' => false,
            'enableStrictParsing' => true,
            'rules' => [
                // ...
            ],
        ],
    ],
]

where

• yii\web\UrlManager::enablePrettyUrl: this property toggles the pretty URL format.
• yii\web\UrlManager::showScriptName: this property determines whether the entry script should be included in the created URLs. For example, in stead of creating a URL /index.php/post/100, by setting this property to be true, a URL /post/100 may be generated.
• yii\web\UrlManager::enableStrictParsing: this property determines whether to enable strict request parsing. If strict parsing is enabled, the incoming requested URL must match at least one of the yii\web\UrlManager::rules in order to be treated as a valid request, or a yii\web\NotFoundHttpException will be thrown. If strict parsing is disabled, when none of the yii\web\UrlManager::rules matches the requested URL, the path info part of the URL will be treated as the requested route.
• yii\web\UrlManager::rules: this property contains a list of rules specifying how to parse and create URLs. It is the main property that you should work with in order to create URLs whose format satisfies your particular application requirement.

Note: In order to hide the entry script name in the created URLs, besides setting yii\web\UrlManager::showScriptName to be true, you may also need to configure your Web server so that it can correctly identify which PHP script should be executed when a requested URL does not explicitly specify one. If you are using Apache Web server, you may refer to the recommended configuration as described in the Installation section.

URL Rules

URL rules are objects responsible for parsing and creating URLs when the pretty URL format is used. You declare the URL rules by configuring them in the yii\web\UrlManager::rules property. The property takes an array with each element specifying a single URL rule. When the yii\web\UrlManager is parsing an incoming request, it examines the rules in the order they are declared and looks for the first rule that matches the requested URL. The matching rule is then used to parse the URL into a route and its associated parameters. Similarly, when the yii\web\UrlManager is used to create a URL, it looks for the first rule that matches the given route and parameters and uses it to create a URL.

The following yii\web\UrlManager::rules configuration declares two URL rules. The first rule matches a URL posts and maps it into the route post/index. The second rule matches a URL matching the regular expression post/(\d+) and maps it into the route post/view and a parameter named id.

[
    'posts' => 'post/index', 
    'post/<id:\d+>' => 'post/view',
]

Info: Only the path info part of a URL is used to match against a rule. The path info of a URL is the part after the entry script and before the query string. For example, the path info of /index.php/post/100?source=ad is /post/100. When performing the matching test, both of the leading and ending slashes in the path info are ignored.

Named Parameters

A URL rule can be associated with a few named parameters. When the rule is used to parse a URL, it will fill these parameters with values matching various parts of the URL. And when the rule is used to create a URL, it will take the values of the provided parameters and insert them into various parts of the URL being created.

To specify a named parameter, embed in the URL pattern with a token <ParamName> or <ParamName:Pattern>, where ParamName specifies the parameter name and Pattern is a regular expression that the parameter value should match. If Pattern is not specified, it means the parameter should match any characters except /.

Let's use some examples to explain how URL rules work. Assume we have declared the following URL rules:

[
    'posts' => 'post/index',
    'post/<id:\d+>' => 'post/view',
    'posts/<year:\d{4}>/<category>' => 'post/index',
]

• Parsing URLs
  • /index.php/posts is parsed into the route post/index using the first rule;
  • /index.php/posts/2014/php is parsed into the route post/index, the year parameter whose value is 2014 and the category parameter whose value is php using the third rule;
  • /index.php/post/100 is parsed into the route post/view and the id parameter whose value is 100 using the second rule;
  • /index.php/posts/php will cause a yii\web\NotFoundHttpException when yii\web\UrlManager::enableStrictParsing is true, because it matches none of the patterns. If yii\web\UrlManager::enableStrictParsing is false (the default value), the path info part posts/php will be returned as the route.
• Creating URLs
  • Url::to(['post/index']) creates /index.php/posts using the first rule;
  • Url::to(['post/index', 'year' => 2014, 'category' => 'php']) creates /index.php/posts/2014/php using the third rule;
  • Url::to(['post/view', 'id' => 100]) creates /index.php/post/100 using the second rule;
  • Url::to(['post/view', 'id' => 100, 'source' => 'ad']) creates /index.php/post/100?source=ad using the second rule. Because the source parameter is not specified in the rule, it is appended as a query parameter in the created URL.
  • Url::to(['post/index', 'category' => 'php']) creates /index.php/post/index?category=php using none of rules. Note that since none of the rules applies, the URL is created by simply appending the route as the path info and all parameters as the query string part.

Parameterizing Routes

Rules may also make use of named parameters as part of a route. Named parameters allow a rule to be applied to multiple routes based on matching criteria. Named parameters may also help reduce the number of rules needed for an application, and thus improve the overall performance.

The following example rules illustrate how to parameterize routes with named parameters:

[
    '<controller:(post|comment)>/<id:\d+>/<action:(create|update|delete)>' => '<controller>/<action>',
    '<controller:(post|comment)>/<id:\d+>' => '<controller>/read',
    '<controller:(post|comment)>s' => '<controller>/list',
]

In the above example, two named parameters are found in the route part of the rules: controller and action. The former matches a controller ID that's either "post" or "comment", while the latter matches an action ID that could be "create", "update", or "delete". You may name the parameters differently as long as they do not conflict with any GET parameters that may appear in your URLs.

Using the above rules, the URL /index.php/post/123/create will be parsed as the route post/create with GET parameter id=123. Given the route comment/list and GET parameter page=2, Yii can create a URL /index.php/comments?page=2.

Parameterizing Hostnames

It is also possible to include hostnames in the rules for parsing and creating URLs. One may extract part of the hostname to be a GET parameter. This is especially useful for handling subdomains. For example, the URL http://admin.example.com/en/profile may be parsed into GET parameters user=admin and lang=en. On the other hand, rules with hostnames may also be used to create URLs with parameterized hostnames.

In order to use parameterized hostnames, simply declare the URL rules while including the host info:

[
    'http://<user:\w+>.example.com/<lang:\w+>/profile' => 'user/profile',
]

In the above example, the first segment of the hostname is treated as the "user" parameter while the first segment of the pat is treated as the "lang" parameter. The rule corresponds to the user/profile route.

Note that yii\web\UrlManager::showScriptName will not take effect when a URL is being created using a rule with a parameterized hostname.

Also note that any rule with a parameterized hostname should NOT contain the subfolder if the application is under a subfolder of the web root. For example, if the application is under http://www.example.com/sandbox/blog, then you should still use the same URL rule as described above without the subfolder sandbox/blog.

Faking URL Suffix

<?php
return [
    // ...
    'components' => [
        'urlManager' => [
            'suffix' => '.html',
        ],
    ],
];

Handling REST requests

TBD:

• RESTful routing: yii\filters\VerbFilter, yii\web\UrlManager::$rules
• Json API:
  • response: yii\web\Response::format
  • request: yii\web\Request::$parsers, yii\web\JsonParser

Customizing URL Rules

yii\web\UrlRule class is used for both parsing URL into parameters and creating URL based on parameters. Despite the fact that default implementation is flexible enough for the majority of projects, there are situations when using your own rule class is the best choice. For example, in a car dealer website, we may want to support the URL format like /Manufacturer/Model, where Manufacturer and Model must both match some data in a database table. The default rule class will not work because it mostly relies on statically declared regular expressions which have no database knowledge.

We can write a new URL rule class by extending from yii\web\UrlRule and use it in one or multiple URL rules. Using the above car dealer website as an example, we may declare the following URL rules in application config:

// ...
'components' => [
    'urlManager' => [
        'rules' => [
            '<action:(login|logout|about)>' => 'site/<action>',

            // ...

            ['class' => 'app\components\CarUrlRule', 'connectionID' => 'db', /* ... */],
        ],
    ],
],

In the above, we use the custom URL rule class CarUrlRule to handle the URL format /Manufacturer/Model. The class can be written like the following:

namespace app\components;

use yii\web\UrlRule;

class CarUrlRule extends UrlRule
{
    public $connectionID = 'db';

    public function init()
    {
        if ($this->name === null) {
            $this->name = __CLASS__;
        }
    }

    public function createUrl($manager, $route, $params)
    {
        if ($route === 'car/index') {
            if (isset($params['manufacturer'], $params['model'])) {
                return $params['manufacturer'] . '/' . $params['model'];
            } elseif (isset($params['manufacturer'])) {
                return $params['manufacturer'];
            }
        }
        return false;  // this rule does not apply
    }

    public function parseRequest($manager, $request)
    {
        $pathInfo = $request->getPathInfo();
        if (preg_match('%^(\w+)(/(\w+))?$%', $pathInfo, $matches)) {
            // check $matches[1] and $matches[3] to see
            // if they match a manufacturer and a model in the database
            // If so, set $params['manufacturer'] and/or $params['model']
            // and return ['car/index', $params]
        }
        return false;  // this rule does not apply
    }
}

Besides the above usage, custom URL rule classes can also be implemented for many other purposes. For example, we can write a rule class to log the URL parsing and creation requests. This may be useful during development stage. We can also write a rule class to display a special 404 error page in case all other URL rules fail to resolve the current request. Note that in this case, the rule of this special class must be declared as the last rule.