Suggest latest PHP 7 usage in the guide [skip ci]

docs/guide/intro-yii.md

@@ -50,8 +50,8 @@ This guide is mainly about version 2.0.
 Requirements and Prerequisites
 ------------------------------
 
-Yii 2.0 requires PHP 5.4.0 or above. You can find more detailed requirements for individual features
-by running the requirement checker included in every Yii release.
+Yii 2.0 requires PHP 5.4.0 or above and runs best with the latest version of PHP 7. You can find more detailed
+requirements for individual features by running the requirement checker included in every Yii release.
 
 Using Yii requires basic knowledge of object-oriented programming (OOP), as Yii is a pure OOP-based framework.
 Yii 2.0 also makes use of the latest features of PHP, such as [namespaces](http://www.php.net/manual/en/language.namespaces.php)

docs/guide/start-installation.md

@@ -152,7 +152,7 @@ Yii's requirements. You can check if the minimum requirements are met using one
   ```
 
 You should configure your PHP installation so that it meets the minimum requirements of Yii. Most importantly, you
-should have PHP 5.4 or above. You should also install the [PDO PHP Extension](http://www.php.net/manual/en/pdo.installation.php)
+should have PHP 5.4 or above. Ideally latest PHP 7. You should also install the [PDO PHP Extension](http://www.php.net/manual/en/pdo.installation.php)
 and a corresponding database driver (such as `pdo_mysql` for MySQL databases), if your application needs a database.
 
 

docs/guide/tutorial-performance-tuning.md

@@ -11,8 +11,8 @@ factors and explain how you can improve your application performance by adjustin
 A well configured PHP environment is very important. In order to get maximum performance,
 
 - Use the latest stable PHP version. Major releases of PHP may bring significant performance improvements.
-- Enable bytecode caching with [Opcache](http://php.net/opcache) (PHP 5.5 or later) or [APC](http://ru2.php.net/apc) 
-  (PHP 5.4 or earlier). Bytecode caching avoids the time spent in parsing and including PHP scripts for every
+- Enable bytecode caching with [Opcache](http://php.net/opcache) (PHP 5.5 or later) or [APC](http://php.net/apc) 
+  (PHP 5.4). Bytecode caching avoids the time spent in parsing and including PHP scripts for every
   incoming request.
 - [Tune `realpath()` cache](https://github.com/samdark/realpath_cache_tuner).