How to add one form field with two separate input fields

Hi, I new to yii framework and I’m trying to create a simple form, one of the fields is the zip code in Portugal which is composed by two components ex. 2000-001 I wanted to have two separate input fields for each number in the zip code (2000 in the first one and 001 in the second one) and then concatenate these two with ‘-’ sign, so in the model it reads as “2000-001”

Something like this:

Thank you