I ran into a problem with using Yii in Chrome: I want to create a form field for a telephone number. I first made it a numberField, but Chrome does not allow the use of "+", which makes this option not possible. However, a textField has limited usability on mobile devices, which have optimizations for filling in numeric fields.
The solution would be to use the type="tel" input field, but Yii has no support for generating that yet, while it seems like a basic piece of functionality.