fixes #6263 and has no problem with PHP Bug:

> it is a PHP bug: https://bugs.php.net/bug.php?id=45543
> Fixed in this commit: php/php-src@22dba2f#diff-7b738accc3d60f74c259da18588ddc5dL2996
>
> Fixed in PHP >5.4.26 and >5.5.10. http://3v4l.org/mlZX7

Fixes #5627: Added `yii cache/flush-schema` console command to flush DB schema cache of a given database connection

fixes #5448

fixes #6164

Fixes #4823 and #6005: `yii message` accuracy and error handling were improved by using PHP tokenizer instead of regular expressions. Removed eval() as well.

fixes #5683

Fixes #4643: Extra options specified in `yii\widgets\Breadcrumbs::links` will be treated as HTML attributes for the generated hyperlinks

fixes #5652

fixes #5601

Fixed `yii\console\controllers\AssetController` breaks CSS URLs in case target file localed at `yii\web\AssetManager::basePath` root

Fixes #5467: Added ability to pass HTML tag options to `asEmail()`, `asImage()` and `asUrl()` methods of `yii\i18n\Formatter`

Fixes #5316: Added `startsWith()` and `endsWith()` to `yii\helpers\StringHelper`. Methods are binary-safe, multibyte-safe and optionally case-insensitive

fixes #5179