You would find having such a need in most Yii Projects. Your database needs a specific format to store date fields, while you may want to display it in different formats to the users on forms and other views.
If you have a form, you sometimes need special validation Rules not included in Yii. Here i share a special rule with you, i just wrote. Maybe you have the case, when a user needs to Fill ou Field A oder the Fields B, C and D.
In Yii 1.x, there was a built in widget CStarRating based on the jquery star rating plugin. There exists no prebuilt solution in Yii2, however the same concepts can be extended using any jquery plugin.
If you are coming over to Yii 2 from Yii 1.x, you may have already read this useful wiki for creating dependent dropdowns.
You can use a similar approach in Yii 2 to do the same. But if you are looking at a prebuilt solution that helps you manage it easier, read along.