To extend the functionality of you web application relative to your requirements you are supposed to use existing yii core libraries or use external libraries. There are some steps to ensure security, uniqueness, modularity, performance and to avoid rework in future.
Sometime its very important to perform many actions/operation with limited time frame for friendly use, select2 provides a lot of such functionality , I just extend it tags functionality to provide a quick use for developer to save time, as I spent much time on it.
You have a multilingual application, and you want the URL of a page to be different for different languages, to account for SEO. The URL for the contact page for example should look like http://something.com/en/contact in english, and http://something.com/de/contact in german. This tutorial describes how to make it happen.
Note that currently selected language is always a part of the URL, and thus available to the application through $_GET. You don't have to use sessions variables to keep track of the language if you don't want to.
Many Yii users ask how to create helper classes and functions, and though there are numerous approaches spread out among the forum and wiki articles, this Tutorial tries to bring it all together in one place.
Sometimes we get lost trying to search by a HAS_MANY relation using CActiveRecord or CActiveDataProvider. This article is a series of drills that try to describe the practical techniques of searching by a HAS_MANY relation.
If you have read this wiki you would be aware of the yii2-detail-view extension and how it offers you an easy way to EDIT and VIEW your model data, toggle these modes, and other features. You can read the extension documentation and/or view a demo of this extension, to understand usage.