From b503dc9ff2d2b528d156b00bffca8c65e30ba148 Mon Sep 17 00:00:00 2001
From: Carsten Brandt <mail@cebe.cc>
Date: Sun, 1 May 2016 03:45:47 +0200
Subject: [PATCH] use ::class also in documentation and configs

- shorter syntax
- native PHP feature, so it does not depend on yii\base\Object
- Does not trigger autoloading anymore
---
 composer.json                                     |  2 +-
 framework/BaseYii.php                             |  2 +-
 framework/base/Component.php                      |  4 ++--
 framework/base/Controller.php                     |  4 ++--
 framework/base/Module.php                         |  8 ++++----
 framework/caching/DbCache.php                     |  2 +-
 framework/caching/MemCache.php                    |  2 +-
 framework/composer.json                           |  2 +-
 framework/console/controllers/AssetController.php |  2 +-
 framework/db/Connection.php                       |  2 +-
 framework/di/Container.php                        | 18 +++++++++---------
 framework/di/Instance.php                         |  6 +++---
 framework/di/ServiceLocator.php                   | 12 ++++++------
 framework/filters/ContentNegotiator.php           |  4 ++--
 framework/filters/HttpCache.php                   |  2 +-
 framework/filters/PageCache.php                   |  6 +++---
 framework/grid/ActionColumn.php                   |  4 ++--
 framework/grid/CheckboxColumn.php                 |  2 +-
 framework/grid/GridView.php                       |  6 +++---
 framework/grid/SerialColumn.php                   |  2 +-
 framework/helpers/BaseMarkdown.php                |  8 ++++----
 framework/i18n/I18N.php                           |  4 ++--
 framework/log/Dispatcher.php                      |  4 ++--
 framework/log/EmailTarget.php                     |  4 ++--
 framework/mutex/MysqlMutex.php                    |  4 ++--
 framework/mutex/PgsqlMutex.php                    |  4 ++--
 framework/rest/ActiveController.php               | 12 ++++++------
 framework/rest/UrlRule.php                        |  6 +++---
 framework/validators/UniqueValidator.php          |  8 ++++++--
 framework/validators/Validator.php                |  4 ++--
 framework/web/CacheSession.php                    |  2 +-
 framework/web/DbSession.php                       |  2 +-
 framework/web/JsonResponseFormatter.php           |  2 +-
 framework/web/Response.php                        |  8 ++++----
 framework/web/UrlRule.php                         |  2 +-
 framework/widgets/FragmentCache.php               |  2 +-
 36 files changed, 86 insertions(+), 82 deletions(-)

diff --git a/composer.json b/composer.json
index 8e5cce7..a137b36 100644
--- a/composer.json
+++ b/composer.json
@@ -61,7 +61,7 @@
         "yiisoft/yii2": "self.version"
     },
     "require": {
-        "php": ">=5.6.0",
+        "php": ">=5.5.0",
         "ext-mbstring": "*",
         "ext-ctype": "*",
         "lib-pcre": "*",
diff --git a/framework/BaseYii.php b/framework/BaseYii.php
index 0f99597..10ade3b 100644
--- a/framework/BaseYii.php
+++ b/framework/BaseYii.php
@@ -307,7 +307,7 @@ class BaseYii
      *
      * // create an object using a configuration array
      * $object = Yii::createObject([
-     *     'class' => 'yii\db\Connection',
+     *     'class' => \yii\db\Connection::class,
      *     'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
      *     'username' => 'root',
      *     'password' => '',
diff --git a/framework/base/Component.php b/framework/base/Component.php
index a7721e1..b29ed87 100644
--- a/framework/base/Component.php
+++ b/framework/base/Component.php
@@ -82,7 +82,7 @@ use Yii;
  * ```php
  * [
  *     'as tree' => [
- *         'class' => 'Tree',
+ *         'class' => Tree::class,
  *     ],
  * ]
  * ```
@@ -413,7 +413,7 @@ class Component extends Object
      *
      * ```php
      * 'behaviorName' => [
-     *     'class' => 'BehaviorClass',
+     *     'class' => BehaviorClass::class,
      *     'property1' => 'value1',
      *     'property2' => 'value2',
      * ]
diff --git a/framework/base/Controller.php b/framework/base/Controller.php
index 0dba943..ced58be 100644
--- a/framework/base/Controller.php
+++ b/framework/base/Controller.php
@@ -92,9 +92,9 @@ class Controller extends Component implements ViewContextInterface
      *
      * ```php
      * return [
-     *     'action1' => 'app\components\Action1',
+     *     'action1' => \app\components\Action1::class,
      *     'action2' => [
-     *         'class' => 'app\components\Action2',
+     *         'class' => \app\components\Action2::class,
      *         'property1' => 'value1',
      *         'property2' => 'value2',
      *     ],
diff --git a/framework/base/Module.php b/framework/base/Module.php
index 8657848..b85508f 100644
--- a/framework/base/Module.php
+++ b/framework/base/Module.php
@@ -76,9 +76,9 @@ class Module extends ServiceLocator
      *
      * ```php
      * [
-     *   'account' => 'app\controllers\UserController',
+     *   'account' => \app\controllers\UserController::class,
      *   'article' => [
-     *      'class' => 'app\controllers\PostController',
+     *      'class' => \app\controllers\PostController::class,
      *      'pageTitle' => 'something new',
      *   ],
      * ]
@@ -417,10 +417,10 @@ class Module extends ServiceLocator
      * ```php
      * [
      *     'comment' => [
-     *         'class' => 'app\modules\comment\CommentModule',
+     *         'class' => \app\modules\comment\CommentModule::class,
      *         'db' => 'db',
      *     ],
-     *     'booking' => ['class' => 'app\modules\booking\BookingModule'],
+     *     'booking' => ['class' => \app\modules\booking\BookingModule::class],
      * ]
      * ```
      *
diff --git a/framework/caching/DbCache.php b/framework/caching/DbCache.php
index 7641644..c37c29b 100644
--- a/framework/caching/DbCache.php
+++ b/framework/caching/DbCache.php
@@ -25,7 +25,7 @@ use yii\di\Instance;
  *
  * ```php
  * 'cache' => [
- *     'class' => 'yii\caching\DbCache',
+ *     'class' => \yii\caching\DbCache::class,
  *     // 'db' => 'mydb',
  *     // 'cacheTable' => 'my_cache',
  * ]
diff --git a/framework/caching/MemCache.php b/framework/caching/MemCache.php
index 6a1207a..a0d3ce3 100644
--- a/framework/caching/MemCache.php
+++ b/framework/caching/MemCache.php
@@ -32,7 +32,7 @@ use yii\base\InvalidConfigException;
  * [
  *     'components' => [
  *         'cache' => [
- *             'class' => 'yii\caching\MemCache',
+ *             'class' => \yii\caching\MemCache::class,
  *             'servers' => [
  *                 [
  *                     'host' => 'server1',
diff --git a/framework/composer.json b/framework/composer.json
index 2dc4d87..ee4c741 100644
--- a/framework/composer.json
+++ b/framework/composer.json
@@ -57,7 +57,7 @@
         "source": "https://github.com/yiisoft/yii2"
     },
     "require": {
-        "php": ">=5.6.0",
+        "php": ">=5.5.0",
         "ext-mbstring": "*",
         "ext-ctype": "*",
         "lib-pcre": "*",
diff --git a/framework/console/controllers/AssetController.php b/framework/console/controllers/AssetController.php
index 841fc70..fd6e916 100644
--- a/framework/console/controllers/AssetController.php
+++ b/framework/console/controllers/AssetController.php
@@ -692,7 +692,7 @@ return [
     // Asset bundle for compression output:
     'targets' => [
         'all' => [
-            'class' => 'yii\web\AssetBundle',
+            'class' => \yii\web\AssetBundle::class,
             'basePath' => '@webroot/assets',
             'baseUrl' => '@web/assets',
             'js' => 'js/all-{hash}.js',
diff --git a/framework/db/Connection.php b/framework/db/Connection.php
index efa1e63..3ddcfc2 100644
--- a/framework/db/Connection.php
+++ b/framework/db/Connection.php
@@ -101,7 +101,7 @@ use yii\caching\Cache;
  * ```php
  * 'components' => [
  *     'db' => [
- *         'class' => '\yii\db\Connection',
+ *         'class' => \yii\db\Connection::class,
  *         'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
  *         'username' => 'root',
  *         'password' => '',
diff --git a/framework/di/Container.php b/framework/di/Container.php
index c312937..03f78e2 100644
--- a/framework/di/Container.php
+++ b/framework/di/Container.php
@@ -72,13 +72,13 @@ use yii\helpers\ArrayHelper;
  * }
  *
  * $container = new Container;
- * $container->set('yii\db\Connection', [
+ * $container->set(\yii\db\Connection::class, [
  *     'dsn' => '...',
  * ]);
- * $container->set('app\models\UserFinderInterface', [
- *     'class' => 'app\models\UserFinder',
+ * $container->set(\app\models\UserFinderInterface::class, [
+ *     'class' => \app\models\UserFinder::class,
  * ]);
- * $container->set('userLister', 'app\models\UserLister');
+ * $container->set('userLister', \app\models\UserLister::class);
  *
  * $lister = $container->get('userLister');
  *
@@ -191,20 +191,20 @@ class Container extends Component
      *
      * ```php
      * // register a class name as is. This can be skipped.
-     * $container->set('yii\db\Connection');
+     * $container->set(\yii\db\Connection::class);
      *
      * // register an interface
      * // When a class depends on the interface, the corresponding class
      * // will be instantiated as the dependent object
-     * $container->set('yii\mail\MailInterface', 'yii\swiftmailer\Mailer');
+     * $container->set(\yii\mail\MailInterface::class, \yii\swiftmailer\Mailer::class);
      *
      * // register an alias name. You can use $container->get('foo')
      * // to create an instance of Connection
-     * $container->set('foo', 'yii\db\Connection');
+     * $container->set('foo', \yii\db\Connection::class);
      *
      * // register a class with configuration. The configuration
      * // will be applied when the class is instantiated by get()
-     * $container->set('yii\db\Connection', [
+     * $container->set(\yii\db\Connection::class, [
      *     'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
      *     'username' => 'root',
      *     'password' => '',
@@ -214,7 +214,7 @@ class Container extends Component
      * // register an alias name with class configuration
      * // In this case, a "class" element is required to specify the class
      * $container->set('db', [
-     *     'class' => 'yii\db\Connection',
+     *     'class' => \yii\db\Connection::class,
      *     'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
      *     'username' => 'root',
      *     'password' => '',
diff --git a/framework/di/Instance.php b/framework/di/Instance.php
index 7d756b5..bfa18eb 100644
--- a/framework/di/Instance.php
+++ b/framework/di/Instance.php
@@ -25,9 +25,9 @@ use yii\base\InvalidConfigException;
  *
  * ```php
  * $container = new \yii\di\Container;
- * $container->set('cache', 'yii\caching\DbCache', Instance::of('db'));
+ * $container->set('cache', \yii\caching\DbCache::class, Instance::of('db'));
  * $container->set('db', [
- *     'class' => 'yii\db\Connection',
+ *     'class' => \yii\db\Connection::class,
  *     'dsn' => 'sqlite:path/to/file.db',
  * ]);
  * ```
@@ -42,7 +42,7 @@ use yii\base\InvalidConfigException;
  *     public function init()
  *     {
  *         parent::init();
- *         $this->db = Instance::ensure($this->db, 'yii\db\Connection');
+ *         $this->db = Instance::ensure($this->db, \yii\db\Connection::class);
  *     }
  * }
  * ```
diff --git a/framework/di/ServiceLocator.php b/framework/di/ServiceLocator.php
index f4c28df..756ad37 100644
--- a/framework/di/ServiceLocator.php
+++ b/framework/di/ServiceLocator.php
@@ -26,11 +26,11 @@ use yii\base\InvalidConfigException;
  * $locator = new \yii\di\ServiceLocator;
  * $locator->setComponents([
  *     'db' => [
- *         'class' => 'yii\db\Connection',
+ *         'class' => \yii\db\Connection::class,
  *         'dsn' => 'sqlite:path/to/file.db',
  *     ],
  *     'cache' => [
- *         'class' => 'yii\caching\DbCache',
+ *         'class' => \yii\caching\DbCache::class,
  *         'db' => 'db',
  *     ],
  * ]);
@@ -146,11 +146,11 @@ class ServiceLocator extends Component
      *
      * ```php
      * // a class name
-     * $locator->set('cache', 'yii\caching\FileCache');
+     * $locator->set('cache', \yii\caching\FileCache::class);
      *
      * // a configuration array
      * $locator->set('db', [
-     *     'class' => 'yii\db\Connection',
+     *     'class' => \yii\db\Connection::class,
      *     'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
      *     'username' => 'root',
      *     'password' => '',
@@ -240,11 +240,11 @@ class ServiceLocator extends Component
      * ```php
      * [
      *     'db' => [
-     *         'class' => 'yii\db\Connection',
+     *         'class' => \yii\db\Connection::class,
      *         'dsn' => 'sqlite:path/to/file.db',
      *     ],
      *     'cache' => [
-     *         'class' => 'yii\caching\DbCache',
+     *         'class' => \yii\caching\DbCache::class,
      *         'db' => 'db',
      *     ],
      * ]
diff --git a/framework/filters/ContentNegotiator.php b/framework/filters/ContentNegotiator.php
index 7d2bfc5..7be7c7b 100644
--- a/framework/filters/ContentNegotiator.php
+++ b/framework/filters/ContentNegotiator.php
@@ -39,7 +39,7 @@ use yii\web\UnsupportedMediaTypeHttpException;
  * return [
  *     'bootstrap' => [
  *         [
- *             'class' => 'yii\filters\ContentNegotiator',
+ *             'class' => \yii\filters\ContentNegotiator::class,
  *             'formats' => [
  *                 'application/json' => Response::FORMAT_JSON,
  *                 'application/xml' => Response::FORMAT_XML,
@@ -64,7 +64,7 @@ use yii\web\UnsupportedMediaTypeHttpException;
  * {
  *     return [
  *         [
- *             'class' => 'yii\filters\ContentNegotiator',
+ *             'class' => \yii\filters\ContentNegotiator::class,
  *             'only' => ['view', 'index'],  // in a controller
  *             // if in a module, use the following IDs for user actions
  *             // 'only' => ['user/view', 'user/index']
diff --git a/framework/filters/HttpCache.php b/framework/filters/HttpCache.php
index 8df842f..f60cad7 100644
--- a/framework/filters/HttpCache.php
+++ b/framework/filters/HttpCache.php
@@ -25,7 +25,7 @@ use yii\base\Action;
  * {
  *     return [
  *         [
- *             'class' => 'yii\filters\HttpCache',
+ *             'class' => \yii\filters\HttpCache::class,
  *             'only' => ['index'],
  *             'lastModified' => function ($action, $params) {
  *                 $q = new \yii\db\Query();
diff --git a/framework/filters/PageCache.php b/framework/filters/PageCache.php
index 81287b7..afd9711 100644
--- a/framework/filters/PageCache.php
+++ b/framework/filters/PageCache.php
@@ -30,11 +30,11 @@ use yii\web\Response;
  * {
  *     return [
  *         'pageCache' => [
- *             'class' => 'yii\filters\PageCache',
+ *             'class' => \yii\filters\PageCache::class,
  *             'only' => ['index'],
  *             'duration' => 60,
  *             'dependency' => [
- *                 'class' => 'yii\caching\DbDependency',
+ *                 'class' => \yii\caching\DbDependency::class,
  *                 'sql' => 'SELECT COUNT(*) FROM post',
  *             ],
  *             'variations' => [
@@ -74,7 +74,7 @@ class PageCache extends ActionFilter
      *
      * ```php
      * [
-     *     'class' => 'yii\caching\DbDependency',
+     *     'class' => \yii\caching\DbDependency::class,
      *     'sql' => 'SELECT MAX(updated_at) FROM post',
      * ]
      * ```
diff --git a/framework/grid/ActionColumn.php b/framework/grid/ActionColumn.php
index 8951cc0..3b15d62 100644
--- a/framework/grid/ActionColumn.php
+++ b/framework/grid/ActionColumn.php
@@ -21,7 +21,7 @@ use yii\helpers\Url;
  * 'columns' => [
  *     // ...
  *     [
- *         'class' => ActionColumn::class,
+ *         'class' => \yii\grid\ActionColumn::class,
  *         // you may configure additional properties here
  *     ],
  * ]
@@ -53,7 +53,7 @@ class ActionColumn extends Column
      * As an example, to only have the view, and update button you can add the ActionColumn to your GridView columns as follows:
      *
      * ```php
-     * ['class' => 'yii\grid\ActionColumn', 'template' => '{view} {update}'],
+     * ['class' => \yii\grid\ActionColumn::class, 'template' => '{view} {update}'],
      * ```
      *
      * @see buttons
diff --git a/framework/grid/CheckboxColumn.php b/framework/grid/CheckboxColumn.php
index 9b5a17d..ad5f6c8 100644
--- a/framework/grid/CheckboxColumn.php
+++ b/framework/grid/CheckboxColumn.php
@@ -21,7 +21,7 @@ use yii\helpers\Json;
  * 'columns' => [
  *     // ...
  *     [
- *         'class' => 'yii\grid\CheckboxColumn',
+ *         'class' => \yii\grid\CheckboxColumn::class,
  *         // you may configure additional properties here
  *     ],
  * ]
diff --git a/framework/grid/GridView.php b/framework/grid/GridView.php
index 5d39f36..30e0380 100644
--- a/framework/grid/GridView.php
+++ b/framework/grid/GridView.php
@@ -141,14 +141,14 @@ class GridView extends BaseListView
      *
      * ```php
      * [
-     *     ['class' => SerialColumn::class],
+     *     ['class' => \yii\grid\SerialColumn::class],
      *     [
-     *         'class' => DataColumn::class, // this line is optional
+     *         'class' => \yii\grid\DataColumn::class, // this line is optional
      *         'attribute' => 'name',
      *         'format' => 'text',
      *         'label' => 'Name',
      *     ],
-     *     ['class' => CheckboxColumn::class],
+     *     ['class' => \yii\grid\CheckboxColumn::class],
      * ]
      * ```
      *
diff --git a/framework/grid/SerialColumn.php b/framework/grid/SerialColumn.php
index 78155b2..ca9ca7d 100644
--- a/framework/grid/SerialColumn.php
+++ b/framework/grid/SerialColumn.php
@@ -16,7 +16,7 @@ namespace yii\grid;
  * 'columns' => [
  *     // ...
  *     [
- *         'class' => 'yii\grid\SerialColumn',
+ *         'class' => \yii\grid\SerialColumn::class,
  *         // you may configure additional properties here
  *     ],
  * ]
diff --git a/framework/helpers/BaseMarkdown.php b/framework/helpers/BaseMarkdown.php
index 07ed299..4409b75 100644
--- a/framework/helpers/BaseMarkdown.php
+++ b/framework/helpers/BaseMarkdown.php
@@ -25,20 +25,20 @@ class BaseMarkdown
      */
     public static $flavors = [
         'original' => [
-            'class' => 'cebe\markdown\Markdown',
+            'class' => \cebe\markdown\Markdown::class,
             'html5' => true,
         ],
         'gfm' => [
-            'class' => 'cebe\markdown\GithubMarkdown',
+            'class' => \cebe\markdown\GithubMarkdown::class,
             'html5' => true,
         ],
         'gfm-comment' => [
-            'class' => 'cebe\markdown\GithubMarkdown',
+            'class' => \cebe\markdown\GithubMarkdown::class,
             'html5' => true,
             'enableNewlines' => true,
         ],
         'extra' => [
-            'class' => 'cebe\markdown\MarkdownExtra',
+            'class' => \cebe\markdown\MarkdownExtra::class,
             'html5' => true,
         ],
     ];
diff --git a/framework/i18n/I18N.php b/framework/i18n/I18N.php
index 9ae858c..6b916e3 100644
--- a/framework/i18n/I18N.php
+++ b/framework/i18n/I18N.php
@@ -57,14 +57,14 @@ class I18N extends Component
         parent::init();
         if (!isset($this->translations['yii']) && !isset($this->translations['yii*'])) {
             $this->translations['yii'] = [
-                'class' => 'yii\i18n\PhpMessageSource',
+                'class' => PhpMessageSource::class,
                 'sourceLanguage' => 'en-US',
                 'basePath' => '@yii/messages',
             ];
         }
         if (!isset($this->translations['app']) && !isset($this->translations['app*'])) {
             $this->translations['app'] = [
-                'class' => 'yii\i18n\PhpMessageSource',
+                'class' => PhpMessageSource::class,
                 'sourceLanguage' => Yii::$app->sourceLanguage,
                 'basePath' => '@app/messages',
             ];
diff --git a/framework/log/Dispatcher.php b/framework/log/Dispatcher.php
index 3caf8f5..58e422b 100644
--- a/framework/log/Dispatcher.php
+++ b/framework/log/Dispatcher.php
@@ -27,12 +27,12 @@ use yii\base\ErrorHandler;
  *         'log' => [
  *             'targets' => [
  *                 'file' => [
- *                     'class' => 'yii\log\FileTarget',
+ *                     'class' => \yii\log\FileTarget::class,
  *                     'levels' => ['trace', 'info'],
  *                     'categories' => ['yii\*'],
  *                 ],
  *                 'email' => [
- *                     'class' => 'yii\log\EmailTarget',
+ *                     'class' => \yii\log\EmailTarget::class,
  *                     'levels' => ['error', 'warning'],
  *                     'message' => [
  *                         'to' => 'admin@example.com',
diff --git a/framework/log/EmailTarget.php b/framework/log/EmailTarget.php
index 659c645..f432dc0 100644
--- a/framework/log/EmailTarget.php
+++ b/framework/log/EmailTarget.php
@@ -23,7 +23,7 @@ use yii\mail\MailerInterface;
  *     'log' => [
  *          'targets' => [
  *              [
- *                  'class' => 'yii\log\EmailTarget',
+ *                  'class' => \yii\log\EmailTarget::class,
  *                  'mailer' => 'mailer',
  *                  'levels' => ['error', 'warning'],
  *                  'message' => [
@@ -67,7 +67,7 @@ class EmailTarget extends Target
         if (empty($this->message['to'])) {
             throw new InvalidConfigException('The "to" option must be set for EmailTarget::message.');
         }
-        $this->mailer = Instance::ensure($this->mailer, 'yii\mail\MailerInterface');
+        $this->mailer = Instance::ensure($this->mailer, MailerInterface::class);
     }
 
     /**
diff --git a/framework/mutex/MysqlMutex.php b/framework/mutex/MysqlMutex.php
index e47a71b..9a2e47e 100644
--- a/framework/mutex/MysqlMutex.php
+++ b/framework/mutex/MysqlMutex.php
@@ -19,11 +19,11 @@ use yii\base\InvalidConfigException;
  * [
  *     'components' => [
  *         'db' => [
- *             'class' => 'yii\db\Connection',
+ *             'class' => \yii\db\Connection::class,
  *             'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
  *         ]
  *         'mutex' => [
- *             'class' => 'yii\mutex\MysqlMutex',
+ *             'class' => \yii\mutex\MysqlMutex::class,
  *         ],
  *     ],
  * ]
diff --git a/framework/mutex/PgsqlMutex.php b/framework/mutex/PgsqlMutex.php
index aa0d9be..88bc512 100644
--- a/framework/mutex/PgsqlMutex.php
+++ b/framework/mutex/PgsqlMutex.php
@@ -20,11 +20,11 @@ use yii\base\InvalidParamException;
  * [
  *     'components' => [
  *         'db' => [
- *             'class' => 'yii\db\Connection',
+ *             'class' => \yii\db\Connection::class,
  *             'dsn' => 'pgsql:host=127.0.0.1;dbname=demo',
  *         ]
  *         'mutex' => [
- *             'class' => 'yii\mutex\PgsqlMutex',
+ *             'class' => \yii\mutex\PgsqlMutex::class,
  *         ],
  *     ],
  * ]
diff --git a/framework/rest/ActiveController.php b/framework/rest/ActiveController.php
index bdef9ea..800923e 100644
--- a/framework/rest/ActiveController.php
+++ b/framework/rest/ActiveController.php
@@ -71,34 +71,34 @@ class ActiveController extends Controller
     {
         return [
             'index' => [
-                'class' => 'yii\rest\IndexAction',
+                'class' => IndexAction::class,
                 'modelClass' => $this->modelClass,
                 'checkAccess' => [$this, 'checkAccess'],
             ],
             'view' => [
-                'class' => 'yii\rest\ViewAction',
+                'class' => ViewAction::class,
                 'modelClass' => $this->modelClass,
                 'checkAccess' => [$this, 'checkAccess'],
             ],
             'create' => [
-                'class' => 'yii\rest\CreateAction',
+                'class' => CreateAction::class,
                 'modelClass' => $this->modelClass,
                 'checkAccess' => [$this, 'checkAccess'],
                 'scenario' => $this->createScenario,
             ],
             'update' => [
-                'class' => 'yii\rest\UpdateAction',
+                'class' => UpdateAction::class,
                 'modelClass' => $this->modelClass,
                 'checkAccess' => [$this, 'checkAccess'],
                 'scenario' => $this->updateScenario,
             ],
             'delete' => [
-                'class' => 'yii\rest\DeleteAction',
+                'class' => DeleteAction::class,
                 'modelClass' => $this->modelClass,
                 'checkAccess' => [$this, 'checkAccess'],
             ],
             'options' => [
-                'class' => 'yii\rest\OptionsAction',
+                'class' => OptionsAction::class,
             ],
         ];
     }
diff --git a/framework/rest/UrlRule.php b/framework/rest/UrlRule.php
index 83b3783..b4dcf54 100644
--- a/framework/rest/UrlRule.php
+++ b/framework/rest/UrlRule.php
@@ -19,7 +19,7 @@ use yii\web\CompositeUrlRule;
  *
  * ```php
  * [
- *     'class' => 'yii\rest\UrlRule',
+ *     'class' => \yii\rest\UrlRule::class,
  *     'controller' => 'user',
  * ]
  * ```
@@ -41,7 +41,7 @@ use yii\web\CompositeUrlRule;
  *
  * ```php
  * [
- *     'class' => 'yii\rest\UrlRule',
+ *     'class' => \yii\rest\UrlRule::class,
  *     'controller' => ['user', 'post'],
  *     'except' => ['delete'],
  * ]
@@ -125,7 +125,7 @@ class UrlRule extends CompositeUrlRule
      * @var array the default configuration for creating each URL rule contained by this rule.
      */
     public $ruleConfig = [
-        'class' => 'yii\web\UrlRule',
+        'class' => \yii\web\UrlRule::class,
     ];
     /**
      * @var boolean whether to automatically pluralize the URL names for controllers.
diff --git a/framework/validators/UniqueValidator.php b/framework/validators/UniqueValidator.php
index 576b1fe..545496a 100644
--- a/framework/validators/UniqueValidator.php
+++ b/framework/validators/UniqueValidator.php
@@ -38,7 +38,11 @@ class UniqueValidator extends Validator
 {
     /**
      * @var string the name of the ActiveRecord class that should be used to validate the uniqueness
-     * of the current attribute value. If not set, it will use the ActiveRecord class of the attribute being validated.
+     * of the current attribute value.
+     * This must be a fully qualified class name.
+     *
+     * If not set, it will use the ActiveRecord class of the attribute being validated.
+     *
      * @see targetAttribute
      */
     public $targetClass;
@@ -106,7 +110,7 @@ class UniqueValidator extends Validator
             $query->andWhere($this->filter);
         }
 
-        if (!$model instanceof ActiveRecordInterface || $model->getIsNewRecord() || get_class($model) !== $targetClass::class) {
+        if (!$model instanceof ActiveRecordInterface || $model->getIsNewRecord() || get_class($model) !== $targetClass) {
             // if current $model isn't in the database yet then it's OK just to call exists()
             // also there's no need to run check based on primary keys, when $targetClass is not the same as $model's class
             $exists = $query->exists();
diff --git a/framework/validators/Validator.php b/framework/validators/Validator.php
index 34bd088..5fbbf3d 100644
--- a/framework/validators/Validator.php
+++ b/framework/validators/Validator.php
@@ -67,7 +67,7 @@ class Validator extends Component
         'image' => 'yii\validators\ImageValidator',
         'in' => 'yii\validators\RangeValidator',
         'integer' => [
-            'class' => 'yii\validators\NumberValidator',
+            'class' => NumberValidator::class,
             'integerOnly' => true,
         ],
         'match' => 'yii\validators\RegularExpressionValidator',
@@ -76,7 +76,7 @@ class Validator extends Component
         'safe' => 'yii\validators\SafeValidator',
         'string' => 'yii\validators\StringValidator',
         'trim' => [
-            'class' => 'yii\validators\FilterValidator',
+            'class' => FilterValidator::class,
             'filter' => 'trim',
             'skipOnArray' => true,
         ],
diff --git a/framework/web/CacheSession.php b/framework/web/CacheSession.php
index 6f69c4c..019161e 100644
--- a/framework/web/CacheSession.php
+++ b/framework/web/CacheSession.php
@@ -26,7 +26,7 @@ use yii\di\Instance;
  *
  * ```php
  * 'session' => [
- *     'class' => 'yii\web\CacheSession',
+ *     'class' => \yii\web\CacheSession::class,
  *     // 'cache' => 'mycache',
  * ]
  * ```
diff --git a/framework/web/DbSession.php b/framework/web/DbSession.php
index 4ba3a9a..9bd1139 100644
--- a/framework/web/DbSession.php
+++ b/framework/web/DbSession.php
@@ -24,7 +24,7 @@ use yii\di\Instance;
  *
  * ```php
  * 'session' => [
- *     'class' => 'yii\web\DbSession',
+ *     'class' => \yii\web\DbSession::class,
  *     // 'db' => 'mydb',
  *     // 'sessionTable' => 'my_session',
  * ]
diff --git a/framework/web/JsonResponseFormatter.php b/framework/web/JsonResponseFormatter.php
index 13fb993..8780f0a 100644
--- a/framework/web/JsonResponseFormatter.php
+++ b/framework/web/JsonResponseFormatter.php
@@ -24,7 +24,7 @@ use yii\helpers\Json;
  *     // ...
  *     'formatters' => [
  *         \yii\web\Response::FORMAT_JSON => [
- *              'class' => 'yii\web\JsonResponseFormatter',
+ *              'class' => \yii\web\JsonResponseFormatter::class,
  *              'prettyPrint' => YII_DEBUG, // use "pretty" output in debug mode
  *              // ...
  *         ],
diff --git a/framework/web/Response.php b/framework/web/Response.php
index 63f842f..cb8aff0 100644
--- a/framework/web/Response.php
+++ b/framework/web/Response.php
@@ -917,11 +917,11 @@ class Response extends \yii\base\Response
     protected function defaultFormatters()
     {
         return [
-            self::FORMAT_HTML => 'yii\web\HtmlResponseFormatter',
-            self::FORMAT_XML => 'yii\web\XmlResponseFormatter',
-            self::FORMAT_JSON => 'yii\web\JsonResponseFormatter',
+            self::FORMAT_HTML => HtmlResponseFormatter::class,
+            self::FORMAT_XML => XmlResponseFormatter::class,
+            self::FORMAT_JSON => JsonResponseFormatter::class,
             self::FORMAT_JSONP => [
-                'class' => 'yii\web\JsonResponseFormatter',
+                'class' => JsonResponseFormatter::class,
                 'useJsonp' => true,
             ],
         ];
diff --git a/framework/web/UrlRule.php b/framework/web/UrlRule.php
index 73aabce..41b82ac 100644
--- a/framework/web/UrlRule.php
+++ b/framework/web/UrlRule.php
@@ -19,7 +19,7 @@ use yii\base\InvalidConfigException;
  *
  * ```php
  * 'rules' => [
- *     ['class' => 'MyUrlRule', 'pattern' => '...', 'route' => 'site/index', ...],
+ *     ['class' => MyUrlRule::class, 'pattern' => '...', 'route' => 'site/index', ...],
  *     // ...
  * ]
  * ```
diff --git a/framework/widgets/FragmentCache.php b/framework/widgets/FragmentCache.php
index 5818fe9..1d007e7 100644
--- a/framework/widgets/FragmentCache.php
+++ b/framework/widgets/FragmentCache.php
@@ -43,7 +43,7 @@ class FragmentCache extends Widget
      *
      * ```php
      * [
-     *     'class' => 'yii\caching\DbDependency',
+     *     'class' => \yii\caching\DbDependency::class,
      *     'sql' => 'SELECT MAX(updated_at) FROM post',
      * ]
      * ```