removed yii\base\Object::className()

it is easy to upgrade existing code and it serves no purpose since
::class syntax is available.

framework/CHANGELOG.md

@@ -5,7 +5,9 @@ Yii Framework 2 Change Log
 -----------------------
 
 - Removed methods marked as deprected in 2.0.x (samdark)
-- Chg #11397: Minimum required version of PHP is 5.6.0 now (samdark)
+- Chg #11397: Minimum required version of PHP is 5.5.0 now (samdark)
+- Chg: Removed `yii\base\Object::className()` in favor of native PHP syntax `::class`, which does not trigger autoloading (cebe)
+
 
 2.0.9 under development
 -----------------------

framework/UPGRADE.md

@@ -18,7 +18,16 @@ php composer.phar global require "fxp/composer-asset-plugin:~1.1.1"
 Upgrade to Yii 2.1.0
 --------------------
 
-* 5.6.0 is the minimum required version of PHP now.
+* The minimum required PHP version is 5.5.0 now.
+
+* `yii\base\Object::className()` has been removed in favor of the [native PHP syntax](http://php.net/manual/en/language.oop5.basic.php#language.oop5.basic.class.class)
+  `::class`. When upgrading to Yii 2.1, You should do a global search and replace for `::className()` to `::class`.
+  All calls on objects via `->className()` should be replaced by a call to `get_class()`.
+
+  You can make this change even before upgrading to Yii 2.1, Yii 2.0.x does work with it.
+
+  `::class` does not trigger auto loading so you can even use it in config.
+
 
 Upgrade from Yii 2.0.7
 ----------------------

framework/base/Object.php

@@ -77,17 +77,6 @@ use Yii;
 class Object implements Configurable
 {
     /**
-     * Returns the fully qualified name of this class.
-     * @return string the fully qualified name of this class.
-     * @deprecated since version 2.1. PHPs `::class` syntax should be used instead.
-     * For object instances, use `get_class()`.
-     */
-    public static function className()
-    {
-        return get_called_class();
-    }
-
-    /**
      * Constructor.
      * The default implementation does two things:
      *