Yii2 framework backup

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URL Management

The concept of URL management in Yii is fairly simple. URL management is based on the premise that the application uses internal routes and parameters everywhere. The framework itself will then translate routes into URLs, and vice versa, according to the URL manager's configuration. This approach allows you to change site-wide URLs merely by editing a single configuration file, without ever touching the application code.

Internal routes

When implementing an application using Yii, you'll deal with internal routes, often referred to as routes and parameters. Each controller and controller action has a corresponding internal route such as site/index or user/create. In the first example, site is referred to as the controller ID while index is referred to as the action ID. In the second example, user is the controller ID and create is the action ID. If the controller belongs to a module, the internal route is prefixed with the module ID. For example blog/post/index for a blog module (with post being the controller ID and index being the action ID).

Creating URLs

The most important rule for creating URLs in your site is to always do so using the URL manager. The URL manager is a built-in application component named urlManager. This component is accessible from both web and console applications via \Yii::$app->urlManager. The component makes availabe the two following URL creation methods:

createUrl($route, $params = [])
createAbsoluteUrl($route, $params = [])

The createUrl method creates an URL relative to the application root, such as /index.php/site/index/. The createAbsoluteUrl method creates an URL prefixed with the proper protocol and hostname: http://www.example.com/index.php/site/index. The former is suitable for internal application URLs, while the latter is used when you need to create URLs for external resources, such as connecting to third party services, sending email, generating RSS feeds etc.

Some examples:

echo \Yii::$app->urlManager->createUrl('site/page', ['id' => 'about']);
// /index.php/site/page/id/about/
echo \Yii::$app->urlManager->createUrl('date-time/fast-forward', ['id' => 105])
// /index.php?r=date-time/fast-forward&id=105
echo \Yii::$app->urlManager->createAbsoluteUrl('blog/post/index');
// http://www.example.com/index.php/blog/post/index/

The exact format of the URL depends on how the URL manager is configured. The above examples may also output:

/site/page/id/about/
/index.php?r=site/page&id=about
/index.php?r=date-time/fast-forward&id=105
/index.php/date-time/fast-forward?id=105
http://www.example.com/blog/post/index/
http://www.example.com/index.php?r=blog/post/index

Inside a web application controller, you can use the controller's createUrl shortcut method. Unlike the global createUrl method, the controller version is context sensitive:

echo $this->createUrl(''); // currently active route
echo $this->createUrl('view', ['id' => 'contact']); // same controller, different action
echo $this->createUrl('post/index'); // same module, different controller and action
echo $this->createUrl('/site/index'); // absolute route no matter what controller is making this call
echo $this->createurl('hi-tech'); // url for the case sensitive action `actionHiTech` of the current controller
echo $this->createurl('/date-time/fast-forward', ['id' => 105]); // url for action the case sensitive controller, `DateTimeController::actionFastForward`

Tip: In order to generate URL with a hashtag, for example /index.php?r=site/page&id=100#title, you need to specify the parameter named # using $this->createUrl('post/read', ['id' => 100, '#' => 'title']).

Customizing URLs

By default, Yii uses a query string format for URLs, such as /index.php?r=news/view&id=100. In order to make URLs human-friendly i.e., more readable, you need to configure the urlManager component in the application's configuration file. Enabling "pretty" URLs will convert the query string format to a directory-based format: /index.php/news/view?id=100. Disabling the showScriptName parameter means that index.php will not be part of the URLs. Here's the relevant part of the application's configuration file:

<?php
return [
	// ...
	'components' => [
		'urlManager' => [
			'enablePrettyUrl' => true,
			'showScriptName' => false,
		],
	],
];

Note that this configuration will only work if the web server has been properly configured for Yii, see installation.

Named parameters

A rule can be associated with a few GET parameters. These GET parameters appear in the rule's pattern as special tokens in the following format:

<ParameterName:ParameterPattern>

ParameterName is a name of a GET parameter, and the optional ParameterPattern is the regular expression that should be used to match the value of the GET parameter. In case ParameterPattern is omitted, it means the parameter should match any characters except /. When creating a URL, these parameter tokens will be replaced with the corresponding parameter values; when parsing a URL, the corresponding GET parameters will be populated with the parsed results.

Let's use some examples to explain how URL rules work. We assume that our rule set consists of three rules:

[
	'posts'=>'post/list',
	'post/<id:\d+>'=>'post/read',
	'post/<year:\d{4}>/<title>'=>'post/read',
]

Calling $this->createUrl('post/list') generates /index.php/posts. The first rule is applied.
Calling $this->createUrl('post/read', ['id' => 100]) generates /index.php/post/100. The second rule is applied.
Calling $this->createUrl('post/read', ['year' => 2008, 'title' => 'a sample post']) generates /index.php/post/2008/a%20sample%20post. The third rule is applied.
Calling $this->createUrl('post/read') generates /index.php/post/read. None of the rules is applied, convention is used instead.

In summary, when using createUrl to generate a URL, the route and the GET parameters passed to the method are used to decide which URL rule to be applied. If every parameter associated with a rule can be found in the GET parameters passed to createUrl, and if the route of the rule also matches the route parameter, the rule will be used to generate the URL.

If the GET parameters passed to createUrl are more than those required by a rule, the additional parameters will appear in the query string. For example, if we call $this->createUrl('post/read', ['id' => 100, 'year' => 2008]), we will obtain /index.php/post/100?year=2008.

As we mentioned earlier, the other purpose of URL rules is to parse the requesting URLs. Naturally, this is an inverse process of URL creation. For example, when a user requests for /index.php/post/100, the second rule in the above example will apply, which resolves in the route post/read and the GET parameter ['id' => 100] (accessible via Yii::$app->request->getQueryParam('id')).

Parameterizing Routes

We may reference named parameters in the route part of a rule. This allows a rule to be applied to multiple routes based on matching criteria. It may also help reduce the number of rules needed for an application, and thus improve the overall performance.

We use the following example rules to 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, we use two named parameters in the route part of the rules: controller and action. The former matches a controller ID to be either post or comment, while the latter matches an action ID to be create, update or delete. You may name the parameters differently as long as they do not conflict with GET parameters that may appear in 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, we 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 hostname may also be used to create URLs with parameterized hostnames.

In order to use parameterized hostnames, simply declare URL rules with host info, e.g.:

[
	'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 path info 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 we 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\web\VerbFilter, \yii\web\UrlManager::$rules
Json API:
- response: \yii\web\Response::format
- request: yii\web\Request::$parsers, \yii\web\JsonParser

URL parsing

Complimentary to creating URLs Yii also handles transforming custom URLs back into internal routes and parameters.

Strict URL parsing

By default if there's no custom rule for a URL and the URL matches the default format such as /site/page, Yii tries to run the corresponding controller's action. This behavior can be disabled so if there's no custom rule match, a 404 not found error will be produced immediately.

<?php
return [
	// ...
	'components' => [
		'urlManager' => [
			'enableStrictParsing' => true,
		],
	],
];

Creating your own rule classes

\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 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 $_GET['manufacturer'] and/or $_GET['model']
			// and return 'car/index'
		}
		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.

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