Yii2 is one of the most popular MVC framework of PHP Why use Yii framework for developing large PHP applications? Why use frameworks at all? The answers are here
The web development process for large custom web application reasonably differs from developing a CMS website or a shopping cart website.
A common CMS or a shopping cart store is never built from scratch because 95% chance is there they made made a similar application. So, a developer starts with an opensource or own built CMS / cart website and simply customizes as per the new requirement. It hardly requires change in database. So newbie developers without any system designing knowledge can build a stunning website or a large store. So it does not require any framework like Yii.
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