CFormatter is one of Yii's core components and used to format values displayed in widgets like CGridView or CDetailView. All classic formats like numbers, text, urls or datetime are supported but you may have to use a formatting rule that isn't built in. Let's say we want to display arrays of strings (like tags associated with a product model). When using CDetailView we would usually make use of PHPs implode function to create a simple string value of all values in the $product->tags array.
With Bootstrap 3 and its inbuilt support in Yii Framework 2.0, you would see quite some new ways of creating HTML markup and styling your site. However, with version 3 of Bootstrap, tooltips and popover are not activated by default on your elements. Assuming you have activated the Bootstrap 3 tooltip plugin - how do you easily enable display of tooltips/popovers across your site?
The popular CListView and CGridView widgets each take a data provider and iterate over each data object produced, calling the user's code to render each row one at a time, and most are familiar with the use of the $data variable to represent the current model object or array.
Ok, you have installed a Yii 2 basic or advanced app for the first time and completed the post install steps. You have picked up a few extensions to install for the first time as well. You would already see a composer.lock file in your application root folder.