Fixes #2734: `FileCache::keyPrefix` defaults to empty string now

framework/CHANGELOG.md

@@ -204,6 +204,7 @@ Yii Framework 2 Change Log
 	- Removed `yii\web\Controller::createUrl` and `yii\web\Controller::createAbsoluteUrl`, use `yii\helpers\Url::toRoute` instead.
 	- Removed `yii\web\Controller::getCanonicalUrl`, use `yii\helpers\Url::canonical` instead.
 - Chg #2691: Null parameters will not be included in the generated URLs by `UrlManager` (gonimar, qiangxue)
+- Chg #2734: `FileCache::keyPrefix` defaults to empty string now (qiangxue)
 - Chg: Renamed `yii\jui\Widget::clientEventsMap` to `clientEventMap` (qiangxue)
 - Chg: Renamed `ActiveRecord::getPopulatedRelations()` to `getRelatedRecords()` (qiangxue)
 - Chg: Renamed `attributeName` and `className` to `targetAttribute` and `targetClass` for `UniqueValidator` and `ExistValidator` (qiangxue)

framework/caching/FileCache.php

@@ -25,6 +25,14 @@ use yii\helpers\FileHelper;
 class FileCache extends Cache
 {
 	/**
+	 * @var string a string prefixed to every cache key. This is needed when you store
+	 * cache data under the same [[cachePath]] for different applications to avoid
+	 * conflict.
+	 *
+	 * To ensure interoperability, only alphanumeric characters should be used.
+	 */
+	public $keyPrefix = '';
+	/**
 	 * @var string the directory to store cache files. You may use path alias here.
 	 * If not set, it will use the "cache" subdirectory under the application runtime path.
 	 */