To change the default route of the application, you should configure the defaultRoute property.

Step 1 − Modify the config/web.php file in the following way.

<?php
   $params = require(__DIR__ . ''/params.php'');
   $config = [
      ''id'' => ''basic'',
      ''basePath'' => dirname(__DIR__),
      ''bootstrap'' => [''log''],
      ''defaultRoute'' => ''site/contact'',
      ''components'' => [
         //other code
?>

Step 2 − Got to http://localhost:8080/index.php. You will see the default contact page.

To put your application in maintenance mode temporarily, you should configure the yiiwebApplication::$catchAll property.

Step 3 − Add the following function to the SiteController.

public function actionMaintenance() {
   echo "<h1>Maintenance</h1>";
}

Step 4 − Then, modify the config/web.php file in the following way.

<?php
   $params = require(__DIR__ . ''/params.php'');
   $config = [
      ''id'' => ''basic'',
      ''basePath'' => dirname(__DIR__),
      ''bootstrap'' => [''log''],
      ''catchAll'' => [''site/maintenance''],
      ''components'' => [
         //OTHER CODE

Step 5 − Now enter any URL of your application, you will see the following.

Creating URLs

To create various kinds of URLs you may use the yiihelpersUrl::to() helper method. The following example assumes the default URL format is being used.

Step 1 − Add an actionRoutes() method to the SiteController.

public function actionRoutes() {
   return $this->render(''routes'');
}

This method simply renders the routes view.

Step 2 − Inside the views/site directory, create a file called routes.php with the following code.

<?php
   use yiihelpersUrl;
?>

<h4>
   <b>Url::to([''post/index'']):</b>
   <?php
      // creates a URL to a route: /index.php?r = post/index
      echo Url::to([''post/index'']);
   ?>
</h4>

<h4>
   <b>Url::to([''post/view'', ''id'' => 100]):</b>
   <?php
      // creates a URL to a route with parameters: /index.php?r = post/view&id=100
      echo Url::to([''post/view'', ''id'' => 100]);
   ?>
</h4>

<h4>
   <b>Url::to([''post/view'', ''id'' => 100, ''#'' => ''content'']):</b>
   <?php
      // creates an anchored URL: /index.php?r = post/view&id=100#content
      echo Url::to([''post/view'', ''id'' => 100, ''#'' => ''content'']);
   ?>
</h4>

<h4>
   <b>Url::to([''post/index''], true):</b>
   <?php
      // creates an absolute URL: http://www.example.com/index.php?r=post/index
      echo Url::to([''post/index''], true);
   ?>
</h4>

<h4>
   <b>Url::to([''post/index''], ''https''):</b>
   <?php
      // creates an absolute URL using the https scheme: https://www.example.com/index.php?r=post/index
      echo Url::to([''post/index''], ''https'');
   ?>
</h4>

Step 3 − Type http://localhost:8080/index.php?r=site/routes, you will see some uses of the to() function.

The route passed to the yiihelpersUrl::to() method can be relative or absolute according to the following rules −

• if the route is empty, the currently requested route will be used.

• if the route has no leading slash, it is considered to be a route relative to the current module.

• if the route contains no slashes, it is considered to be an action ID of the current controller.

The yiihelpersUrl helper class also provides several useful methods.

Step 4 − Modify the routes View as given in the following code.

<?php
   use yiihelpersUrl;
?>

<h4>
   <b>Url::home():</b>
   <?php
      // home page URL: /index.php?r=site/index
      echo Url::home();
   ?>
</h4>
 
<h4>
   <b>Url::base():</b>
   <?php
      // the base URL, useful if the application is deployed in a sub-folder of the Web root
      echo Url::base();
   ?>
</h4>
 
<h4>
   <b>Url::canonical():</b>
   <?php
      // the canonical URL of the currently requested URL
      // see https://en.wikipedia.org/wiki/Canonical_link_element
      echo Url::canonical();
   ?>
</h4>
 
<h4>
   <b>Url::previous():</b>
   <?php
      // remember the currently requested URL and retrieve it back in later requests
      Url::remember();
      echo Url::previous();
   ?>
</h4>

Step 5 − If you enter the address http://localhost:8080/index.php?r=site/routes in the web browser, you will see the following.